Thanks for that, I was with @Blademonkey until now.It's because there were different blade pitches from different manufacturers, typically these tended to be 1.687â€, 1.682†& 1.680â€, in addition some had different ‘ Notch width' ( what was referred to as a tab)
Personally I haven't had a problem with them (whoops jinxed) and I like the way the Karve CB has incorporated the display into their design.