These are great because they are (almost) indefinitely reusable. The manufacturer says you can get ~150 uses but we're still counting. Cold water, light soap and dry them and these things can be used over and over and over and over again. 

This box is a three pack with a small, medium and large sheet with dimensions shown below. You select the color and number of packs.

Small Size:: 8X7 inches (20X17cm)

Medium Size:: 11X10 inches (28X25m)

Large Size:: 14X13inches(36X33cm)