I have no data on bigger ronstan furlers... All i know is my friend tried to save money by purchasing the small Ronstan drum on bottom (i have seen them on small jibs like a DART, and work well) and small spinning part for the top (RONSTAN ROLLER FURLING SWIVEL (EYE\EYE)) of the forestay and he hates both parts. his jib wont furl without a ton of pressure and grief.. and wishes he paid the extra money for the Harken SWIVEL HI-LOAD and FURLING DRUM HI-LOAD