Hope Disc brake adaptors are silver and laser etched with fit information.Adds 20mm Rotor Diameter to your 51mm IS CaliperFor example a 160mm native caliper will require 180mm rotorWill not work with 20mm thru Axle Marzocchi ForksAdds 20mm of disc rotor diameter to dedicated IS calipers for use on post mount forks or frames (i.e a 160mm caliper would require the use of a 180mm rotor)Item SpecificationsRotor Size180,200,220mmCaliper Type51mm I.SBrake Caliper Mount51mm FrontFor Rotor DiameterFront 180,Front 220,Front 200Frame/Fork Mount74mm Post