#4154B - Launching Compartment LE (M4A16-1 Launch Unit , Red Dot at bottom), comes complete as an assembled unit of parts:

#4150/4151 - Locking Pins
#4152A - Shell Ejector Spring
#4153B - Ejector
#4154B - Launching Compartment LE
#4155 - Spring
#4156 - Magazine Rod Sleeve
#4157 - Magazine Rod
#4164 - Cartridge Damping Rubber Sheet
#4183 - Top Bar
#4184 - Pull Bar
#4185 - Top Bar Locking Pin
#4186 - Top Bar Locking Pin
#4187 - Top Bar Spring