Harley Davidson 2 piece Big bore cylinder kit. You will receive a Milwaukee 8 plastic cylinder fixture with bore diameter 4.250 ” I.D. The other fixture is for Twin cam 88 with bore diameter 4.00 ” I.D. Cylinders fixture allows the flow bench technician to flow test cylinder heads on your flowbench. They have dowel pins to increase repeatability when mounting the heads to the fixture, 5 inch square mounting holes flange fits Superflow style flow bench and comes with sealing gaskets and hardware, black satin finish. Other bore sizes available.