The Quench Dome pistons sold by UEM come in a number of varieties, some are for different engines but within those engine sizes they also offer quench domes in different heights... Typically .070 and .140.... The .070 is generally an easy drop in piston when running typical open chamber heads that haven't been milled excessively... It can give effective but rarely ideal quench.... The .140 dome virtually always requires machine work to fit the chamber without crashing the dome into the head... But it can archive ideal quench.... As I stated previously, usually that requires machining the chambers of the heads because as cast it is common to see variations in the chamber depth... So you set the heads up on the mill & equalize the chamber depth... You need to mock up the engine to verify how far the domes are above the deck... Now you have a number for the piston dome height to be set to... So all the pistons get machined to the required dimension... And then comes balancing since the pistons obviously don't weight what they originally did...