My J, K, & L frames
J Frame- Small 5 Shot Revolver
K Frame- Medium 6/7 Shot Revolver
L Frame- Medium 6/7/8 Shot Revolver
N Frame-Large Revolver
Their are some other variations of frame sizes but I just wrote out the common ones.
Think of it like the Glock line up on the common calibers Full-Size, Compact, Sub-Compact.