The T-10 troop chest reserve parachute is an emergency-type parachute used with the T-10C and MC1-1B/C main parachutes. It is designed to be activated by the parachutist using a rip cord in the event of a main canopy failure. Pulling the ripcord opens the pack and releases a spring loaded, 40 inch diameter pilot chute which in turn pulls the main canopy out of the pack tray. The main canopy is 24 feet in diameter and has a 20 inch circular vent at the apex. The packed parachute attaches to two D-rings on the front of the T-10C harness. The T-10 reserve has a rate of descent from 15-22 feet per second, depending on the weight of the parachutist. The weight of the packed parachute is 12 lbs.
Source: US Army FM 57-220 Static Line Parachute Techniques and Training.