Piston rings suit Norton ES2 16H +0.020 oversize (set of 3), 79.5mm bore. Made by Gandini (GPM). Suits Norton models 16H, 18, 20, ES2, CS1, 30 from 1931 to 1955. RRing height 1.58mm (0.062inch), 4mm (0.157inch) Original Norton part number: 9182; A2/161 - piston ring x 2 for 16H, 18, ES2, 30 9183; A2/162 - scraper piston ring x 1 for 16H, 18, ES2, 30