Phoenix Mfg. Company, Inc. V Idler Pulleys

Standard V Idler Pulleys
all have 5/8" bores which can be reduced with bushings -

Idler Pulley Bushings
Bushings for use with idler pulleys - sleeve and shoulder types - reduces bore to 1/2" or 3/8"
Not for use with drive pulleys.

Ecomomy V Idler Pulleys
Suitable for applications such as many types of lawn & garden equipment - bearings to 6000 RPM - all have 3/8" bores