SwissStop is offering Center Lock lockrings to got with their impressive Catalyst disc rotors. This design has been optimized for Center Lock offers a secure hold and perfect fit with the Catalyst, but is also fully compatible with most Center Lock rotors. The system that makes it simple to remove and install a rotor in short time. Most road and gravel disc brake wheelsets feature the Center Lock spline system and utilize a 12 or 15mm thru-axle diameter, which is what SwissStop makes this model for. These lockrings are what is referred as the external serration design, and meant to interface with a 16T/44-45mm (OD) threaded external bottom bracket cup tool, which is a common option sold by Park Tool and other bike tool makers.