General purpose cassette idler tyres tires Hitachi etc pack of 2

These are brand new tyres that a tech asked me to have made for him

It seems they are common in many of the more consumer brands

For now I have these Sizes and they are sold as a pair

16mm OD x 6mm IDx 2.1mm Thick  S1767

20.5mm OD x 10.5mm x 2.1mm Thick S1768

 Photo just for illustration