These high compression pistons for 2007-'17 HD® CVO 110 models including Twin Cooled® except 2017 touring models feature a 12.5cc raised dome to achieve a compression ratio of 10.6:1. Higher compression is a key factor in increasing performance, but it's only part of the solution. Not satisfied with 86 horsepower from your CVO 110 engine? Neither were we! Fortunately, we can show you how to make that big hog really run. Here's how. Install an S&S® performance exhaust and air cleaner - a must for any performance upgrade. Install a set of S&S® 585 bolt-in cams and tune the EFI system - produces over 107 horsepower. Increase the compression ratio from the stock 9.3:1 to 10.6:1 with these S&S® high compression pistons - brings the horsepower up to 114.