Prometheus Spring Combo Set (Includes MS100/ MS110/ MS120/ MS135)
Metal Construction
MS100/ MS110/ MS120/ MS135 Power Up
Non-linear, irregular pitched designed to ease wear and tear on your gearbox
Heat-treated for greater strength and consistent compression 
Anodized paint for reduced wear and tear, minimal flaking
Suitable For AEG Rifle Airsoft Guns

MS spring rates are based on the rough meters per second on a 0.2g BB. You can expect roughly 100 M/S (328 FPS) +/- 5M/S on a MS100 spring. the M/S or FPS can vary considerably due to the entire build setup, so please keep this in mind when choosing a springs.