Zodiac W13061 O-Ring for 1-Piece Cap Replacement for Select Zodiac Nature2 Cartridges<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>O-ring for 1-piece cap replacement</li><li>Fits Zodiac Nature2 Cartridges professional G vessel model W25904 and A vessel model W20040</li><li>Also fit Zodiac Nature2 Premium M cartridge</li></ul></div><img src="http://ecx.images-amazon.com/images/I/41OQt%2BL-A%2BL.jpg" noproxy>