40%
It's blow or smack. 40% purity of either is second tier and most likely to NOT kill the occasional user.
Most people come here because of A Vigilante thinking 40% means a blow job, it just means blow ( or smack ). Unfortunately some drop out screen writer did a search for abuse related terms and stumbled on some elementary school kids definition about swallowing, so now we're all stuck here in the quagmire of a misused 40% slang term making its way into pop culture. In the movie 40% means head because he thinks she's a prostitut; for the rest of us it's just a way to get through the day.