World Source Partners Sun Pottery Classic Ceramic 2-piece Bird Bath with Light Green finish has a Unique strong locking device (not plastic!). All of our glazed pottery and bird baths are fired in gas kilns. These are SIGNIFICANTLY more environmentally friendly than the large standard wood fired "Dragon" kilns used by most of our competitors. The "Dragon" kilns burn a huge amount of rubber-wood at each firing which is very bad for the environment and doesn't provide even firing for the product. Our gas Kilns ensure more even colors and better quality product because the temperature is controllable; unlike that in the wood fired kilns. Durable frostproof construction (up to -4 degrees f.)