Natural River Pebbles Round Pebbles Creates a Natural Riverbed Appearance Easy to Clean Exo Terra Turtle Pebbles are smooth river pebbles formed over time in fast-moving rivers. The smooth pebbles prevent injury to bottom-dwelling turtles or those searching for Food. The color and pattern variations create a natural riverbed appearance. Exo Terra Small Turtle Pebbles (PT3830) are ideal for turtles with a shell diameter of 4"/10 cm or less. To prevent accidental ingestion in turtles with a shell diameter larger than 4"/10 cm, use Exo Terra Large Turtle Pebbles (PT3833). You can easily clean and reuse Exo Terra Turtle Pebbles by soaking and disinfecting them in a large bucket of water for 15 minutes, then rinsing until all visible particles are removed and the water is clear. Round Pebbles (8-10 mm / 0.3"-0.4"), safe for all turtles up to 4" or 10 cm.