EMI 451 COMPLETE HP EMI THUNDER S PIPE SYSTEM FOR SMALL BLOCK CHEVYA perfect solution for exiting exhaust below swimsteps, these EMI systems enable the exhaust to exit underwater at idle keeping them quiet when you want it most. Adjust the outlet position by changing the size of the connection hose. The 16 long riser is a must with High Performance camshafts to prevent reversion (water injection). Complete systems come with all of the necessary bolts, gaskets and fittings. Standard with black Fusioncoated finish