Mrs t2p rode an Air 50R back in the day
still on the bike (pictured)
she has not ridden this bike in a while
Yeah, they made them in a variety of shapes. The 40R is the narrowest, then the 40M is wider and the 40W is wider still. Somewhere along the line, they added a recess for pressure relief, which is what 5 out of my 6 have. Works a treat!