Tascam Porta one Porta two Capstan drive belt in 2 sizes

For the popular little Tascam Porta one and Porta two ( not 02) and maybe a few others in that series as the transport is pretty common in these units. I have seen 2 types of belts fitted, both seem to work, ok but you may want to use what was originally ,fitted they are the same length

One is 4mm wide.

One is 6mm wide.