The Piston Spring is an essential component installed within your P-series Booster Assembly, enabling reliable cycling when paired with a P-series piston on a tilting-barrel handgun. This replacement part is crucial for maintaining optimal functionality. The Piston Spring is included by default and ships inside the booster housing and piston for the Odessa, Ghost and Mojave models. Additionally, the SD500 Booster Assembly comes with a booster spring already installed, ensuring seamless operation right out of the box.