Need to know the weight of the 8 iron head and then the wedges you are putting them in to be more accurate. Basically there are 10 cycles per full flex. 2 grams equals approximately 1 cycle. So if your 8 iron head weight is 276 grams and you sand wedge is 296 grams, that is 20 grams difference. 20 grams equals 10 cycles. The stiff 8 iron shaft in the SW head that weighs 20 grams heavier than the 8 iron head will play a full flex more flexible, or to the R flex.