Approx. 7 cm of adjusting length on the rail of the B17's. If you need more rail consider buying a Rivet - I have the Rivet Pearl and have 12 cm rail so more flex for adjusting. My sits are really narrow - 80 mm center to center so I thought the Pearl would be to wide until I rode it and realized the wiggle room was ideal for me. The B17 regular has a similar width so don't shy away from that either. I like a shorter "skirt" (the side), another reason for picking the Pearl. Like us, most reputable places offer a six month return policy on leather saddles as we know how every body is different. Good Luck, let me know if I can help.