Our GT2 pulley and belt combination provide you with much more precision and anti-backlash properties than other non round tooth profile timing pulleys. The GT2 pulley we machine can be used with 6mm width GT2 belt. It's a good choice for all kinds of machines. 3D printing is just one of these applications. These pulleys will fit 5mm smooth rod and 5mm motor shafts like those found on our NEMA17 Motors.