Brother Nidan, I'm not surprised you were getting razor burn with the setting of 9. I have tough old whiskers, and 5 on the Fat Boy and 6 on the Slim and the Black Beauty are a perfect combination of efficiency and comfort for me. I do 3 pass shaves, and I'm generally a "set it and leave it" guy.I kept my Slim at 9 (with Feather blades because I’d run out of everything else) for years, don’t even remember how I came to the conclusion that 9 was the setting for me. I semi retired it because it was giving me razor burn. Then recently I got back into thinking (ok obsessing) about shaving, razors, technique etc. I replaced my long depleted supply of Astra SPs and tried the Slim with one using the 5 setting. The result was a near perfect 3 pass shave with zero irritation. So for me at the moment, it’s setting 5.