Description The Robert Axle Kid Trailer Axle KID219 – Surly 12 x 177 MDS will allow you to attach a hitch-mounted trailer to your Surly Wednesday. This axle is for use with Surly MDS or Gnot Boost axle system with 12×177 hub standard bikes. This 12mm thru axle from Robert Axle will fit any trailer that has two wheels & a single point of attachment. Including all the two-wheeled child, pet and cargo trailers from Thule, Chariot, Burley, Instep, Carry Freedom & more. Robert Axle want you to share your love of cycling with your kids. Their axle’s will allow quick & secure attachment of your trailer to your favourite bike. Your bike’s stock thru-axle is not strong enough to haul your precious cargo! But Robert Axle’s are 3 to 4 times stronger than the stock axle that will come with your bike. Making their axle ends from Their stainless steel axle will provide a safe and secure attachment point for your trailer. Kid Trailer Axle KID219 – Surly 12 x 177 MDS / Gnot Boost features: Specifically designed to fit the Surly Wednesday. Using the bolt from your stock Surly axle, the derailleur end of the Robert Axle is internally threaded. The disc brake side of this Robert Axle however, has an engineered mount for your trailer hitch that will be permanently attached. Compatible with Burley, Carry Freedom, Chariot/Thule, Croozer, Instep, and many more. The axle shaft is CNC machined 7075 aluminium and hard black anodized for rugged durability. Axle end is stainless steel, which allows for mounting of the hitch provided with your trailer. The threads are M10x1 (metric). Hardware for attachment of the hitch is included; the hitch is not. No special tools required. Design allows for installation or wheel removal using your standard 5mm hex key / wrench.