Thule Prologue Fork Mount Carrier Lockable skewer with single-side adjustment to secure the bike to the carrier for stable and secure bicycle transport(lock sold separately) Single-wall aluminum tray fits bicycle wheelbases up to 48" and tire widths up to 2.6" Compatible with most 9mm disc brakes Works with 15mm, 20mm and left forks with Adapter (53015, 53020, 530l-sold separately) Fits Thule square bars and round bars only