Sorry for the delay, I've been very busy these 2 months -_-
This one is a two-piece pulley for a HTD-5M transmission. It matches with the holes of the Street Wheel and the Off-Road Wheel, links below.
This Pulley supports a 15mm width htd-5m Belt.
To install this pulley onto the wheel you need:
3 M4*30mm Allen (Hex socket) Screws
3 M4 Self-Locking Nuts
Put the nuts into the hexagonal sockets of the rim and screw all together as the picture shows. Easy ;)