[Kevin Sevcik]

The pressure cs. diameter function is probably highly non-linear once you reach the size of the nylon and start trying to expand that. All the same we whipped out a ball pump to hook up to the trackball after it was inflated and it read something less than 2 psi. Probably 1. So there will be some additional weight. I imagine the manufacturing variances will compound the weight fluctuations from air pressure with slightly thicker, heavier balls requiring even more air to inflate. Overall, though, I wouldn't expect for than +/- .25 lb variation out to 3 SDs