Castle Fit Corp v. Friend Enterprises LLC

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Castle Fit Corporation (Delaware)
  • Defendant: Friend Enterprises LLC (Delaware)
  • Plaintiff's Counsel: Smith, Katzenstein & Jenkins, LLP
• Case Identification: Castle Fit Corp. v. Friend Enterprises LLC, 1:26-cv-00588, D. Del., 05/21/2026
• Venue Allegations: Venue is asserted based on the defendant being a Delaware LLC with its principal place of business in Delaware, and having committed alleged acts of patent infringement in the district.
• Core Dispute: Plaintiff alleges that Defendant's "Flex Friend" branded fitness device infringes a patent related to a multimodal fitness bar.
• Technical Context: The technology concerns consumer fitness equipment that integrates a bar with a fabric resistance element to facilitate a range of stretching, mobility, and strength-training exercises.
• Key Procedural History: The complaint alleges that Defendant had actual notice of the asserted patent and its infringement as of October 30, 2025, following communications related to an infringement complaint lodged with Amazon.com. Plaintiff allegedly provided Defendant with an exemplary claim chart on that date. The complaint further alleges that after Amazon removed the accused product, Defendant expanded its sales into other online retail channels, including Walmart.com. The asserted patent is a continuation-in-part of a prior patent, sharing its specification family.

Case Timeline

Date	Event
2020-10-28	'119 Patent Priority Date (via parent application No. 17/082,451)
2022-07-12	U.S. Patent No. 11,383,119 Issued
2025-10-30	Alleged date of Defendant's actual notice of the '119 Patent
2025-12-XX	Alleged removal of Accused Product from Amazon.com (early December)
2026-04-24	Date of Walmart product page capture referenced in complaint
2026-05-19	Date of Walmart product page screenshot depicted in complaint
2026-05-21	Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 11,383,119 - "Multimodal Fitness Bar" (Issued July 12, 2022)

The Invention Explained

• Problem Addressed: The patent's background section is concise, stating only that "Fitness bars are known. Resistance bands are known" '119 Patent, col. 1:11-12 The summary of the invention, however, suggests an underlying problem of needing multiple pieces of equipment to perform a wide variety of exercises and stretches '119 Patent, col. 1:50-52
• The Patented Solution: The patent describes an integrated fitness device that combines a "bar assembly" with a "resistance assembly," which is a flexible fabric sheet '119 Patent, abstract '119 Patent, col. 1:17-23 A key aspect of the solution is an opening in the fabric sheet designed to receive a user's foot, which enables the user to create resistance between their hands gripping the bar and their foot in the sheet, facilitating various stretches like hamstring and plantar fascia stretches '119 Patent, col. 1:30-48 '119 Patent, Fig. 9 '119 Patent, Fig. 10
• Technical Importance: The invention claims to provide a single, compact device capable of supporting a "myriad [of] exercises and stretches" '119 Patent, col. 1:51

Key Claims at a Glance

• The complaint asserts independent claim 1 Compl. ¶29
• The essential elements of independent claim 1 are:
  • A multimodal fitness bar comprising one or more gripping members and a resistance assembly.
  • The gripping members and resistance assembly are attached.
  • The resistance assembly is a sheet with a proximal portion, a distal portion, and an opening between them.
  • The distal portion of the sheet is "curled" when in an unfurled configuration.
  • The distal portion is "configured to interface with the Achilles heel of a user."
• The complaint notes that the infringement analysis is without prejudice to the assertion of additional claims ('119 Patent, Compl. ¶30).

III. The Accused Instrumentality

Product Identification

• The "Flex Friend Yoga Pilates Stretching Strap" (the "Accused Product") Compl. ¶21

Functionality and Market Context

• The Accused Product is described as a stretching device sold through online marketplaces, including a "FriendCo" storefront on Walmart.com Compl. ¶21 Compl. ¶22 A screenshot of the product page describes it as a "Non-elastic stretching strap" with "Ergonomic grip handles" and an "Integrated foot support design" Compl. ¶17 The complaint alleges the Accused Product competes directly with Plaintiff's "CastleFlexx" product in the same consumer market and retail channels, and that its lower price point ($99.99 vs. $238.00) undercuts Plaintiff's sales and inhibits expansion into new retail channels like Walmart Compl. ¶16 Compl. ¶23 A side-by-side comparison image provided in the complaint juxtaposes the patent's Figure 1, Plaintiff's genuine product, and an image of the Accused Product from its Walmart listing Compl. ¶27

IV. Analysis of Infringement Allegations

'119 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
one or more gripping members and a resistance assembly;	The Accused Product comprises ergonomic grip handles and a non-elastic stretching strap.	¶17; ¶21	col. 10:11-12
wherein the one or more gripping members and the resistance assembly are attached;	The Accused Product's strap is attached to a bar that includes the grip handles. This attachment is shown in a product image.	¶17; ¶27	col. 10:13-15
wherein the resistance assembly is a sheet and includes: ... an opening disposed between the proximal portion of the sheet and the distal portion of the sheet;	The Accused Product's strap is described as a "sheet-form resistance assembly" and features an "Integrated foot support design" which is alleged to be the claimed opening.	¶17; ¶21	col. 10:16-24
when the sheet is in an unfurled configuration, the distal portion of the sheet is curled;	The complaint alleges the Accused Product has a "curled distal portion." The product image in the complaint shows the foot-holding portion having a curved shape.	¶21; ¶27	col. 10:25-27
the distal portion of the sheet is configured to interface with the Achilles heel of a user.	The complaint alleges the Accused Product's curled distal portion is "configured to interface with the Achilles heel of a user."	¶21	col. 10:28-30

• Identified Points of Contention:
  • Scope Questions: A central dispute may arise over whether the Accused Product's "Integrated foot support design" Compl. ¶17 meets the claim limitations of a "curled" distal portion that is "configured to interface with the Achilles heel of a user." The litigation may explore whether this requires a specific structure designed for heel capture, or if a generic foot loop is sufficient.
  • Technical Questions: The complaint's allegation that the Accused Product has a portion "configured to interface with the Achilles heel" Compl. ¶21 is a functional claim. A key technical question will be what evidence demonstrates that the accused structure is specifically "configured" for this purpose, as opposed to being a general-purpose loop that may incidentally contact a user's heel.

V. Key Claim Terms for Construction

• The Term: "curled"

  • Context and Importance: This term describes the required shape of the sheet's distal portion. Its construction will be critical in determining whether the shape of the Accused Product's foot holder literally infringes. Practitioners may focus on this term because the visual evidence suggests a potential difference in the degree or nature of the "curl" between the patent's figures and the accused device Compl. ¶27
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The term is not explicitly defined, suggesting it should be given its plain and ordinary meaning, which could encompass any non-flat or arcuate shape.
    • Evidence for a Narrower Interpretation: The specification states that the distal portion of the loop "may curl towards the user" and hang in a "relatively horizontal configuration" to facilitate interfacing with the foot '119 Patent, col. 6:36-41 This language, along with depictions in figures like 5A, 5B, and 10, may support an argument that "curled" implies a specific, functional geometry intended to capture the heel.

• The Term: "configured to interface with the Achilles heel of a user"

  • Context and Importance: This is a functional limitation that defines the purpose of the curled distal portion. The dispute will likely center on whether the Accused Product's design meets this functional requirement.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party could argue that any structure that makes contact with the user's Achilles heel area during a stretching exercise is "configured" to do so, giving the term a broad functional scope.
    • Evidence for a Narrower Interpretation: The specification describes the benefit of securing the user's heel to stretch the plantar fascia without needing straps over the front of the ankle '119 Patent, col. 6:51-62 Furthermore, it describes the "distal portion of loop 517 being wrapped behind user's heel 1001" '119 Patent, col. 9:7-9 '119 Patent, Fig. 10 This may support an interpretation that "configured" requires a specific design that actively and intentionally secures the heel, rather than just incidentally touching it.

VI. Other Allegations

• Indirect Infringement: The complaint's sole count is for direct infringement under 35 U.S.C. § 271(a) Compl. ¶29 While the prayer for relief requests an injunction against indirect infringement, the body of the complaint does not plead specific facts to support claims of inducement or contributory infringement Compl. Prayer D
• Willful Infringement: The complaint alleges that Defendant's infringement is willful and deliberate based on pre-suit knowledge Compl. ¶31 It asserts Defendant gained actual knowledge of the '119 Patent and its infringement on October 30, 2025, after Plaintiff responded to Defendant's inquiry with an exemplary claim chart Compl. ¶31 The complaint further alleges that Defendant continued to sell the Accused Product after receiving this notice and, after being removed from Amazon.com, expanded its sales to other platforms like Walmart.com, which is characterized as "egregious, wanton, and in conscious disregard of Castle Fit's rights" Compl. ¶¶32-33 Compl. ¶36

VII. Analyst's Conclusion: Key Questions for the Case

This case appears to center on the convergence of patent claim language with the design of a competing consumer product. The key questions for the court are likely to be:

• A core issue will be one of definitional scope: Can the functional claim language requiring a "curled" distal portion "configured to interface with the Achilles heel" be read to cover the "Integrated foot support design" of the Accused Product? The outcome may depend on whether this language requires a specific structure intentionally designed for heel capture, as suggested by patent embodiments, or if it encompasses any generic foot loop that performs a similar function.
• A second key question will be one of culpability: Does the alleged timeline of events-including Defendant's initial contact, Plaintiff's provision of a claim chart, and Defendant's subsequent move to a new sales platform after being delisted from Amazon-support a finding of willful infringement? The court's determination will hinge on the evidence presented regarding Defendant's state of mind and actions after receiving notice.