These Axle Studs thread into the Aluminum center axles of our BMX High Flange (Original) hubs, as well as our Classic Mountain Bike hubs. They are machined in our shop in the USA of 4140 Chrome Moly & heat-treated for strength. Sold in pairs Hub not included 3/8 front can also be used for high flange BMX Front or rear hub 3/8 rear (MTB) has a stud with a smaller "locknut" for the drive side to clear the cassette lockring.