Check the listing for details. Self Sink Weighted Single 8.5" Air Diffuser for Pond & Lake Aeration Subsurface. Condition: New. Listed at 88.98 USD. Features:★Made of high-quality rubber diaphragm and heavy-duty 304 stainless steel base, this aeration diffuser is durable with low maintenance. ★Quick self-sinking diffuser could sink to the bottom of ponds or lakes, stable and steady, without extra force. ★Compatible with WRSTER-TECH pond aerators. This dual membrane diffuser is best to use with WRSTER-TECH air pump compressors to increase functionality and greater airflow to the diffuser. ★Produces a high volume of multiple bubbles to mix the oxygen in the water and improve water circulation. ★We offer one year warranty for our product, and free return or replacement within 30 days. Please contact us directly through eBay MESSAGE if you have any problems. We will reply to you ASAP and offer you help.