The illustration shows thruster assemblies as used in the automatic system, with solenoid valves at the ends. The manual system used proportional control throttle valves operated by the astronaut’s control handle.
To operate, the thrusters expelled hydrogen peroxide over a catalyst bed, which caused the fuel to decompose and produce
Mercury spacecraft photo shows a set of yaw thrusters with 1-pound and 24-pound thrusters from the automatic system, and a 24-pound thruster from the manual system.
This 1-pound thruster is a type used on Friendship 7. The design was modified for the Aurora 7 mission (Spacecraft 18), as detailed in the list below, to reduce heat to the solenoid valve and to eliminate problems with screen failure.
Compare the Mercury 24-pound thruster with the Gemini 25-pound thruster and the Apollo 100-pound thruster (in photo below).