Approx outside 23mm ; inside 18mm. (please choose your favorite color).Front 16 ; rear 24 holes. One front and one rear wheelset and 1pair. 6 bearing hubs, front 2 bearing, rear 4 bearing, 9mm. Axle, front hub 74mm, rear hub 130mm width.
Taiwan MADDUX anodized rims, Double-layer butt rivets. Can use for 8/9/10/11 speed freewheel. Folding bike / Small wheel bike / BMX bike. Passed Europe EN14766 Standards and the JAPAN JIS Standards.