"Y-Style" - These are designed to help keep socks up and shirts tucked. They have a single clip for the sock and two clips for the shirt.
"Straight" - These also help keep socks up and shirts tucked, but instead use 4 individual stays, usually clipped towards the front and back of the shirt and socks.
"Stirrup" - These are designed to comfortably keep the shirt tucked in. A single loop goes around the foot, while two clips connect the the shirt. They are made of a softer material than the others. They don't help socks much, though.
All have metal clips with a rubber button that holds the clip in place.
NOTE: the main picture is not to scale (it is actually three individual pictures that we put together to represent the different products)