A plural component spray gun (1) is designed for spraying quick setting materials such as foams, polyurea and the like. Towards this end, the gun (1) is designed so as to be easily serviceable with a minimum of tools. For example, the side seal cartridges (18) and (20) may be installed and removed without tools by removing the retaining ring (9) and then extracting them from the fluid housing (11). Those cartridges (18) and (20) are easily disassembled and cleaned. Similarly, the fluid housing (11) may be removed from the handle/body (1) by unscrewing the lock ring (7) by hand.