I think the smallest size for the Bobcat is M15, which is what I have. I do NOT get as much oxy out of that as I do from tanks even
. I do only boro myself, and there's no question there are times I'd like to go even hotter... but the M-15 is good for most small boro, small marbles and sculpture. I wouldn't even consider a M-10 for boro and bobcat... you won't be able to make spacers I think.