HTH, 6 Pack, 13.3 OZ, Shock Treatment Bag, Effective, Multi-Purpose Product That Sanitizes, Clarifies, Helps Prevent Algae In Your Pool, Convenient, Easy To Use, Won't Over Stabilize Your Pool, For Crystal Clear Pool Water, Follow Our HTH 4 Step Pool Care Program: Step 1: Test & Adjust Pool Water Balance, Step 2: Sanitize, Step 3: Shock Treat Your Pool At Least Once A Week, Step 4: Add Algaecide Regularly.