Lockrings

Lockrings - quite handy to stop your sprocket falling off.

Hub threads

Like everything else on bikes, different manufacturers have historically used different threads for their lockrings. Most have thankfully now settled on a 1.37" x 24tpi thread - but not all.

A 1.37" x 24tpi lockring won't fit a Campag or Phil Wood hub - you'll have to splash out on the more expensive Campag lockring.