I was on the web looking for frame parts.........canti bosses, in particular.....and noticed some sites were stating the offset of the boss. I can understand what they mean by that, but how is this determined? IOW, how does one know what they need? I've already run a few searches without much luck in answers. Maybe it's my choice of keywords..........I dunno. But, could someone help? I'd like to put some on my Lotus Elite 700c.