Last night we went to Walmart to purchase chlorine in anticipation of pool opening in a week or so. The 121 oz store brand bottle was 6% strength for $1.97. I bought 6 bottles. Today at Giant they had 128 ounce bottles “Guaranteed Value” for $1.49 each but no indication of strength. Seems next time I will go to Giant, unless someone knows that the Giant brand is much lower strength?