From our friends at Hardcase Performance:
The HCP Bolt Lock-R keeps pulley/sprocket bolts from being able to loosen up and back out of the wheel hub.
Hard Case Bolt Lock-R
The Hard Case Bolt Lock-R assembly is designed to keep sprocket/pulley bolts from loosening up (i.e. backing out, rotating counter clockwise) and causing costly damage or worse. The pulley/sprocket bolts are held in place by the Bolt Lock-R Keys. The Hard Case Bolt Lock-R does not require any additional modifications to your final drive or rear hub. The Hard Case Bolt Lock-R is a direct bolt on product. You will need to source the proper pulley/sprocket bolts for your application.
The Hard Case Bolt Lock-R fits all HD mag wheels as well as 2006 to current wire wheels. This version will not work with Sportster models, the Hard Case Bolt Lock-R for Sportster models will be available very soon!