There are some light Rota wheels, like Slipstreams which come in at 5.1kgs in a 15 x 6.5". OZ Ultraleggera's at a shade under 5kgs in 15x7.0. Don't think you can get the older Superleggera anymore, they were 4.9kgs in 15x7.0.
Team dynamic do some light rims, such as Pro Race 1, but I think they're closer to 6.5kgs a wheel and in 7" also.
Nothing much comes close to that unless you break into the forged territories and that gets expensive quickly. I'm not a fan of them but Rotas are a good price for the weight if you find a style that you like.
