Complex sentence: The sockets attach to the ratchet through a square fitting that locks onto them and come in four common sizes: 1/4 inch, 3/8 inch, 1/2 inch, and 3/4 inch.
Split into simpler sentences: The sockets attach to the ratchet through a square fitting. The fittings come in four common sizes: 1/4 inch, 3/8 inch, 1/2 inch, and 3/4 inch.