1 1/8 inch to 1 inch Headset Reducer (Pair)for ISO Headsets Will not work on BMX headsets with 32.5 ID We have here a pair of precision head tube reducers. These reducers will allow you to install any standard 1 inch ISO headset on your 1 1/8 inch frame.NOT for BMX style headsets with a 32.5mm ID Machined from solid 6061-T6 aluminum stock 34mm Outside Diameter 30.2 Inside Diameter