Wanted, Black nimbus double quick release seat post clamp 28.6mm
Are you sure about 28.6mm ? this is not standard (25.4 / 27.2) for unicycling !
Clamp sizing is considering the outer diameter of the seat tube and not the inner diameter or seatpost size. So a 28.6mm clamp fits a 25.4mm seatpost and 31.8mm clamp fits a 27.2mm seatpost.
Nimbus DoubleQuick Aluminium construction clamp in Blue, Green, Orange, Red and white, with black levers and the the Nimbus logo laser etched on the front,
These clamps will only fit frames with a external diameter of 28.6mm