Abstract: An apparatus for improving the aerodynamic performances of conventionally spoked bicycle wheels or the like, the apparatus comprising a pair of rings (10) being adapted to be located one on either side of the spokes of the wheel and abutting against the wheel's inside rim at their most radial outward portion (11) and extending inwardly towards the wheel's axle. The rings (10) are releasably mated at the most radial inward portion (13) with apertures (16) formed when so mated, The apertures (16) are formed about the spokes when located thereon with the outer surface (12) of the pair of rings (10) forming an aerodynamic surface extending radially inwardly from the wheel's inner rim.