November 10, 2019 - I have a Princess Auto 3/8 pneumatic belt sander. they have an odd size belt, 3/8x12-9/16 . the common size for these is 3/8x13" Some reports say the 13" belts work fine, and for me they sort of did, but a bit loose . the shaft didn't extend far enough nor was the spring tight enough to create enough outward pressure to tighten the belt.