On-One make an assortment of sprockets and spacers necessary for finding the ideal chainline if you're running a cassette hub single-speed. The Groove Armadas are probably the best solution for most riders; their 3/32in sizing means you can still run a normal geared chain instead of changing to a fat BMX set-up. The flat teeth allow the chain to run better than on wobbly toothed cassette sprockets, and the grooves below the teeth are a gesture towards mud clearance. Sprockets come in 16, 17, 18, 20 and 22-tooth sizes.
Product "9874" does not exist or you do not have permission to access it.