That's true. Here is their size list, all in inches:
SQUARE: 3/8, 1/2, 5/8, 3/4, 1, 1 1/4, 1 1/2, 2, 3
RECTANGULAR: 1 1/4 x 1, 1 1/2 x 1, 1 1/2 x 2, 2 x 1, 2 x 3
They come in green, blue, black, red, yellow or clear, so you can color-code your stuff at the same time you waterproof and segregate it. Not that I've ever done that ...