What size bullet in diameter does wolf ammunition use in 8mm?

Assuming you're referring to the 7.92x57 (a.k.a., 8x57) Mauser cartridge, it depends on whether it's the I or IS cartridge. The I cartridge has a diameter of 8.08mm (.318 inches), and the IS cartridge has a diameter of 8.20mm (.323 inches). Which one you refer to depends specifically on which Wolf ammo you had in mind - Wolf doesn't actually manufacture ammo, they simply market it. Ammo comes from a number of sources, including the Tula Cartridge Works in Russia (Wolf, Wolf Military Classic), Privi Partisan in Serbia (Wolf Gold), and others.