These pebbles are made from Polystyrene (PS) and are non-toxic, tasteless, and non-radioactive. They have a dimension of 0.8"-1.2" and can glow for approximately two to three hours in the dark after full sun exposure, or up to 10 hours if charged by lamp light. Price drops from $31.98 to just $21.99. Shipping is free with Amazon Prime or is otherwise a flat $6 per order.