It's widely applied in step extruder as a part of filament drive system.
It's also can be used as 5mm bore V Groove Idler Pulley for fishing line 625VV or V625ZZ ball bearing.
Inner Diameter(ID):    5mm
Outer Diameter(OD):   16mm
Thickness:                 5mm
U Groove Deepness:   0.5mm
U Groove Width:         1.5mm
Weight:                    45g/10PCS