Product Description Has your old hub failed, or do you need a new hub to complete an old DIY project you have sitting around? One of our replacement steel hub sets is what you can rely on to get you back up and rolling again. The 4"" x 4"" go-kart axle hub is most commonly found on go-karts using 8"" wheels. Although these hubs are fit for Yerf-Dog 'karts, these are compatible with many quads, ATVs, and trikes that use this same hub. These hubs feature four lug nuts, and the hubs are 2-3/4"" long. The inner bore is milled for a 1/4"" axle key. The most common style for gokarts features a 1"" inner (or inboard) shaft diameter with the axle turned down to a 3/4"" outer diameter. Please note that our AlveyTech 4"" x 4"" Go-Kart Live Axle Hubs with 1"" to 3/4"" Step-Down are sold in packs or as a single. Pick from our single, 2-pack, or 4-pack option for convenience. Specs are going to be important when selecting a new hub. Please refer to our following specs to see if this will be the right hub for your project.  SPECIFICATIONS: Diameter: 5"" (125 mm) Length: 2-3/4"" Keyway & key size: 1/4"" (6.5 mm) Inboard axle bore diameter: 1"" Outboard axle bore diameter: 3/4"" Mounting lugs (across): 4"" Mounting lugs (side by side): 2-7/8"" Lug length: 1-1/16"" Lug thread: 1/2x20