ISM PN 4.1 Saddle - Chromoly BlackISM PN 4. 1 Saddle Chromoly Black. The PN 4. 1 Performance Narrow saddle is similar in design to the PN 4. 0 with increased padding for those looking to soften their ride. Sit bone contact points are wider at 125mm to better accommodate a range of pelvic body positions. Like the other PN saddles the PN 4. 1 offers superb thigh and hamstring clearance which allows for more rider body movement around the seat and is great for diving into fast corners.