I don't know who "they" are, but the GL1800 and the F6B saddles are very much different. I can't set on a GL saddle comfortably(to small) with my 6'5" 36" inseam sized frame, but can set for a short while on the F6B saddle, but it is still to low for me and why I use and promote the custom made Russel Day-Long as the one and only saddle for my tender ass.