RM Stihl .325 non safety is all I run. I never know what I'll be cutting and holds an edge pretty good. That plus my dealer does buy 2 get 1 free so 3 chains are around $50..325 is the best for a 50CC saw IMO. However I have always ran 3/8" and a 16" bar on my 50cc saws. Mostly because when I was doing alot of cutting I purchased chain by the roll and it was easier to have only one size on hand. The other advantage to 3/8" is the ability to use Stihl RM chain for cutting really dirty wood. I'm not sure if Stihl ever made non saftey RM chain in .325. If they did I never saw it.