Check the listing for details. Scooter GY6 150cc High Performance 3mm or 4mm Stroke Crankshaft (CHOOSE ONE). Condition: New. Listed at 109.99 USD. 3mm and 4mm Stroker Crankshafts for the GY6 150cc engines made in Taiwan by Shengee. 3mm is the easiest to install. Will require a spacer. (Available in our ebay store) 3mm uses the stock timing chain and studs. 4mm is more difficult to install and is more for people that are experienced. 4mm requires a spacer, uses stock chain and may require you to shave down the piston. AGAIN... 4mm IS A LOT HARDER TO INSTALL. If you are not experienced... choose 3mm SHIPS USPS LARGE FLAT RATE BOX Large FRB cost $21.50 to ship...3mm and 4mm Stroker Crankshafts for the GY6 150cc engines made in Taiwan by Shengee. 3mm is the easiest to install. Will require a spacer. (Available in our ebay store) 3mm uses the stock timing chain and studs. 4mm is more difficult to install and is more for people that are experienced. 4mm requires a spacer, uses stock chain and may require you to shave down the piston. AGAIN... 4mm IS A LOT HARDER TO INSTALL. If you are not experienced... choose 3mm <NO SPACER, STUDS OR CHAIN INCLUDED> SHIPS USPS LARGE FLAT RATE BOX Large FRB cost $21.50 to ship...