Replaces Novarossi .21 Part Number 16800 14 x 25.8 x 6 ABEC-3 Stainless Steel Ball Bearing Silicon Nitride Ceramic Balls & Light Nylon Cage High Quality ABEC-3 Bearings, Stainless Steel, Nylon Cage with Silicon Nitride ceramic balls for Novarossi .21& .28 engines, inner diameter is 14mm, outer diameter is 25.8mm, and width is 6mm.