phil wood they make different sizes I used a 73x122 good have gone to a 135 I had a sealed bottom bracket left over in Shimano. Look closely at these upon install {use blue lock tight , order there special socket] it is totally possible to move it to the left of the bike or the right. Centering the cranks is a piece of cake! Hope this helps, when I peddled everywhere in my day It was very important to me to be set evenly on a bike . There are a lot of bikes uneven at the bottom bracket these days. ONE OF MY BIGGEST PEIVES.....Phil Wood - ALL: Aspire VeloTech Secure Online Store They are really quit fool proof too I have peddled 6000 miles on these before with no probs at all changed it out cause I was bored!