I bought Nortons Grit. Garnet grit was availablle as well but, the 10 kg bucket was twice the size of the 10 kg Norton grit. I said to the assistant "l'll take this one it is denser". He said "but they are both the same weight". Another level of denseness entered the equation. The Norton grit is $20 cheaper than Garnet.
Thanks for all your suggestions.