Hi I have a pair of 6825 but can't seem to get on with them I use a Bergeon tool 6767 find it a lot easier hope this helps, but buy a cheep watch to practice on, I changed the strap on my rolex this morning in 10 mins,
I've been using the Official Geneve tool for a couple of years. I can only recommend it, it's good quality tool and works well for my occasional integrated bracelet/strap changes.