Superior Threads L-Style Pre Wound Bobbin Assortment Prewound Bobbins Masterpiece Thread 35ct w/Purple Lavender Bobbin Saver Cardboard-sided prewound bobbins may be used with the cardboard sides on or with the sides removed. 35 colors from Superior Threads Frostings Line. L style prewound bobbins with Superior Threads MasterPiece Thread. MasterPiece is #50 100% extra-long staple Egyptian-grown cotton. 80 yds per bobbin. Tucked into a BobbinSaver for safe keeping and instant access to all colors!