A saw mill chain is not what you want for normal cutting. A saw mill chain is designed to cut along the length of a log, not cut through it. If you want a 20 inch chain for your saw, just get a count of the drive links you need and read the information on pitch and gauge that is stamped into the bolt end of your bar. Then go out and find a matching chain from Husky, Stihl, Oregon, Carlton or one of the other chain manufacturers. Actually I am not so sure that Husky actually makes chain but the ones with their brand on them work fine.
That price on E-bay is way higher than a good cross cutting chain would be. I think I paid about $14 each for a group of 6 order of Husky chains in 72dl, .050 gauge, 3/8 pitch, full chisel tooth. Bought individually I would expect to pay maybe $20 each locally.