Shimano XT SM-RT81 Disc Brake Rotor Lock Ring and Washer - Walmart.com
Shimano XTR SM-RT99/ XT SM-RT81 1 or 2 Center Lock Disc Brake Lock Ring W/Washer | eBay
SHIMANO SM-RT81 LOCK RING &WASHER - SoCal Bike - Oceanside, Carlsbad and north San Diego county's favorite bike shop, Bicycle and ebike rentals, sales, and service