First Base Mitts are Called a 'mitt' because it lacks individual fingers, they are designed specifically for first base and are not used anywhere else on the field. Between 12-13 inches, these mitts have deep pockets and a wide, curved outside edge to give the first baseman an edge in scooping thrown baseballs out of the dirt. The larger size also gives other infielders a bigger target to throw to. It is not uncommon or inappropriate to use outfield baseball gloves when playing first base.
Also fingerless, the catcher's mitt is the most specialized type of baseball glove on the field. Heavily padded and uniquely shaped to direct pitches into it's deep pocket, the catcher's mitt presents the pitcher with a wide target to throw at while providing the catcher's hand with maximum protection. Though other baseball gloves are measured from the tip of the index finger to the heel of the glove, catcher's mitts are measured by circumference, usually between 32 and 34 inches around.