All-City QR x 135 mm 6-Bolt Disc Bicycle Rear Hubs
About All-City - "All-City's goal is to make a significant contribution to the equipment and culture of urban cycling. This is not a cash in, this is not a fad, this is our life, our love, our community and our dream. We are a company of riders making products for other riders."
This is hub spacing and is the width of the hub. It must match your frame specifications.
This should correspond to the type of brakes you have on the bike.