Hmm, maybe a typo here. You say, "This is the double spring version that will not work with Gen 4 and Gen 5 only...." but then say it's also not for Gen 3?
Check with McCUTCHEON'S on Wisner street in Frederick. It’s been a while but I’ve bought metal 55 gallon drums from them in the past. They were pretty cheap too!
