20g chlorine tablets that have a significantly higher pH than other tablets (ie they are significantly less acidic) and so dramatically reduce the risk of acid damage to your hot tub seals and equipment. 

Prior to using this product adjust the PH levels to the ideal range of 7.2 - 7.6 to promote bather comfort, protection of spa plant equipment and effective chemical use. These smaller chlorine tablets are designed for use with chlorine feeders or with floating dispensers. They will slowly erode over a period of 3-5 days depending on the water flowing over them.

As they release chlorine relatively slowly it may be necessary to shock dose or oxidise prior to their use to first establish some chlorine more rapidly. Ideal chlorine levels are between pools 1-3 mg/1 (ppm) and spas 3-5 mg/1 (ppm) as tested by a test kit or strips.