Swk/L/N-201 Pro-Spring Kit For S&W K,L,N Frame Revolver - Pro-Spring Kit #swk/L/N-201 For S&W K, L, N Frame Revolver

From Brownells.com

Reduced power kit with lighter than stock Power Rib mainspring plus 13, 14, & 15 lb. rebound springs for precise tuning. Lightens trigger pull and gives superior smoothness and consistency of both double & single action pull. Mfg: Brownells