Looks like Yale Lite in the Murray's catalog. I use Yale Lite for both the mainsheet and jib sheet (3/8 in. and 5/16 in., I think) and it's great: does not tangle or soak up water. Once the cover on the sheets wear out, I use them for righting lines (Specra/Dyneema core is still good).

Rick sells a similar product, Sampson Ultra-Lite, in the Cat Sailor on-line store. 3/8 in. Sampson Ultra-Lite

Does anyone use sheets of Dyneema/Polypro braid such as Yale Conception or 100 percent Polypro braid such as Marlow Marstron? Any good?