A simple but very effective shoulder just under the head of the bolt serves to distribute the load and make this the strongest 7075 Aluminum or Titanium 6AL-4V Chainring bolt on the market.
While all other bolts on the market use a 5mm internal hex, Rennen chose 4mm to provide more material and increase overall strength further by 8.5%
Regular length (SHORT) has been optimized to work with most gear crank combinations
XL (LONG) is specifically designed for thick crank spiders like Answer Accelerator cranks. XXL is made for RaceFace SixC Carbon cranks.