I bought a few of the Frontier straws,a few yrs.ago,& Stupidly didn't pay attention to the instructions,I had read prior to using one.I got a Huge mouthful of charcoal,gritty funk upon my 1st sip from one of these,& then it tapered off gradually,thereafter.They worked well for me,After my Hazing of stupidity,lol! Live & Learn!