inner and outer, that's flash! most get the outer and some expanding foam in the gap behind, lol.
i have 4 grinders so i don't have to keep changing wheels. 1- grinding, 1- cutting, 3- flapwheel and 4- twist knot wire wheel. you really save time when the job means cut a bit, grind a bit, cut a bit etc etc. and they're just the 4 1/2" ones, i have 2 9" for cutting metal and a a diamond wheel for stone/blocks etc. plus a 12" chop saw of course. you can never have too many power toys.you know its a transit when you see 2 grinders on the job