HTH 67008 Calcium Hardness Increaser， 4 lb<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>Hth calcium hardness increaser， 4 lbs.</li><li>Low calcium hardness may cause the pool water to be corrosive， resulting in damage to pool surfaces and equipment</li><li>Raises calcium hardness levels. Prevents corrosion of metal &amp; plaster surfaces. Compatible with Salt Systems</li></ul></div><img src="http://ecx.images-amazon.com/images/I/41cwVdoAVvL.jpg" noproxy>