I have that exact set, and man, do they work well. Just remember, the 1" isn't 1", it's 1.35" the 3/4" is actually 1.08" They are for electricians. They are to make holes in the metal circuit boxes for conduit. Hence the larger than listed sizes. Just for reference:

1/2" = .86" or 22.2mm
3/4" = 1.08" or 27.5mm
1" = 1.35" or 34.4mm
1 1/4" = 1.69" or 42.9mm

but once you add grommet to the hole, it's real close.