Custom-made PETG (Reef Safe) display plugs that fit perfectly in egg crate. I personally use them in my WYSIWYG system to help organize frags.
To order simply pick the quantity, plug color, and letter color. During checkout, you will see a "notes" section. Please put what letters or numbers you would like. You can have up to two numbers or two letters per plug.
Letters: FF, O, 1, 3, 10