The 17 and 18 were not measured by me they were measured by redrobin on freshly calibrated measuring scales.
The VWR wheel is a quoted weight from the manufacturer.
Redrobin's wheels are both Mk5 BBS though, aren't they?
I can only comment on what I weighed, in my garage.
I was surprised to find the VWR wheel lighter than their site said...and the comparitive weights for the Ronal Monza and BBS CH were only what I weighed, on my digital bathroom scales, in my garage.