Head strap holder replacement part for VO2 max test mask. The original strap holders are quite prone to break (acrylic) and when they break, it is necessary to buy a whole new mask (very expensive). With this 3D model, you can replace the acrylic parts with almost no cost and protect your investment. Print recommendation: I printed using nylon. 100% infill, brim adhesion (12mm). After printed, heat the parts with a heat gun or hot water and bend them about 45 degree on the center. Tested on extra small and small size masks.