I cut one dome off a different piston I never used YEARS ago to experiment and then REBCO machine did the remaining mods to make these up the compression to 12.2ish and Line-2-Line coated the skirts because they were for 4.390 bore.(block is 4.395) What was nice is that over the phone, Rebco was able to know that the pistons could be lightened based on the information i gave him, this allowed swapping pistons without a requiring a rebalance!