Mofeez Bike Bicycle Trailer Coupler Attachment Angled Elbow for Instep & Schwinn Bike Trailers Price: $7.39 (as of 04/03/2021 12:04 PST- Details)

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UNIVERSAL DESIGN—It fits almost all bikes and all Schwinn and InStep brand trailers (such as all series AA, AB, AC AD, AE, AG, AH, AI).The diameter of the hole attach to your bike is 1/2″ and the outer diameter of the part that attaches to the axle is 1″.
WELL MADE AND STRONG—Made of high quality steel.Solid construction and well built. Coated with powder paint which made it blends into your bike perfectly even when no trailer is connected.