The peg in the bottom is designed to fit nicely into egg crate, it will also fit nicely into a small crevice or hole in your live rock. (Some customers drill 3/8" holes throughout their new live rock, to provide future resting places for frag plugs).
The top is about 1" in diameter and sports a layer of reef sand that helps corals and coralline algae to adhere more quickly, it also looks more natural then aragocrete.
Reef Plugs are designed to support Acropora, Montipora Digitata and other thin branchy species of coral.
*Discounts exclude products from these manufacturers with MAP (minimum advertised price) rules: Ecotech Marine, Neptune Systems (Apex), Coral Vue (Reef Octopus, Maxspect), Aqua Illumination and Aqua UV.