ISM PN 3.1 Saddle - Chromoly BlackISM PN 3. 1 Saddle Chromoly Black. The ISM PN 3. 1 has more padding for riders who prefer a slightly softer ride. With a 120mm rear end and and tapered edges the PN 3. 1 is so comfortable it will disappear underneath you. The PN 3. 1 offerings superb thigh and hamstring clearance. This allows for more rider body movement around the seat and is great for diving into fast corners. Like all ISM saddles the PN 3. 1 is nose less and designed to remove