Compatible with stock cylinders and heads, gives stock compression ratio. 8.5:1 CR. Piston pin weight 97gr. Head type: Dome 0.656 / Dome -57cc. Compression height 1.450. Bore 3.4375″ / Stroke 3.969″ (3-31/32). Rod length 7.440 / Cyl. Comes with T6 heat treated 390 Hypereutectic cast pistons with 16% silicone levels which enables running a very tight clearance for longevity and hardly any piston noise. Note: Top compression ring will need additional clearance. 41-78 74/1200cc Knuckle, Pan, Shovel (NU). We will accept your request at our earliest opportunity. This includes Republic Of Ireland. Please do not ask us to lower the value of goods this is illegal and we do not want to get involved in this kind of activity.