Gauge: Gauge denotes the number of lead balls of bore diameter that equal one pound; 20 gauge corresponds to a nominal bore diameter of about 0.615 in.

Length: Common shell lengths include 2¾ in (70 mm) and 3 in (76 mm).

Shot Sizes: Payload types include birdshot (small pellets for birds and small game), buckshot (larger pellets for defensive use and some hunting), and slugs (single projectile for larger game).

Applications: Common uses include upland bird hunting (e.g., pheasant, grouse, quail), sport shooting (trap/skeet/sporting clays) and general small-game hunting. Compared with 12 gauge, 20 gauge generally offers lighter firearms and reduced recoil, at the cost of lower maximum payload and often slightly reduced pattern density at longer ranges.