This is a prototype for a gage used to align and set the grip distance for an ASTM D638 Tensile sample with thickness <3.5mm. I created it based on experience with tensile testing of fiber reinforced plastic ASTM D638 Type I samples. I wanted a good way to center the specimens and get the grips the correct distance apart.

The model has been printed in PLA and tested. It should also work in PETG or ABS. It was designed in FreeCAD. There's no commercial equivalent that I'm aware of, as the procedure is usually simply measuring the grip distance. Print cost should be under $1 USD.