This design is a system of flexible attach for GT2 Belt. I use it to fix the belt to the heated bed of my printer. It adapts to a M5 screw in the center. I designed a flexible attach because the rigid one i used previously led to artifacts when the movement direction of the bed was reversed.
Two versions of the model are provided, "Belt attach flexible" is a tight fitting and requires some adjusting but yield a strong and tight fitting part while "Belt attach flexible large tolerances" has looser tolerances.