Ratchet—Ratchet-Mechanism guns only apply pressure to the cartridge while you pull the trigger. They’re good for use with thin materials that require flow control.

Smooth—Smooth-Mechanism guns apply more consistent pressure to the cartridge, so flow continues between trigger pulls. These guns are often used with thick materials that require strength to dispense and maintain flow.

Adjustable Thrust Ratio—Guns with an adjustable thrust ratio let you use the same gun for sealants and caulks with different consistencies. Use a higher thrust ratio to evenly dispense thicker, more viscous sealants and a lower ratio for thinner sealants.

Dual Cartridge Capacity—Guns with a dual cartridge capacity give you more time between refills and let you mix two-part compounds.

Thrust Ratio—To choose a thrust ratio, consider the thickness of the material—thinner materials such as silicone and latex flow easily, so choose a low thrust ratio gun. Thick materials such as urethanes and epoxies require more power to dispense, so choose a high thrust ratio.