This is a heaver and longer spring than the Gold spring for the level 10. The red spring will produce a much stronger Level 10 effect causing the bolt to decelerate even faster during a breach "incident". This spring allows the use of even more brittle paint while reducing the chance of a pinch. The flip side is this spring requires more energy to operate the marker thus reducing the air efficiency and sometimes causing a regulator piston failure in older pistons or the inability to reach velocity in some classic 68 Automags. A gold spring is the most efficient set-up and typically produces acceptable results. Use the red spring if you need more Level 10 sensitivity. Use of red spring may require higher tank input pressure to achieve full velocity.