Just put the half inch washer around the bottom of the injector and install it the same way the old ones came out. Half inch washers worked for me but its not an ideal setup. Be sure to replace the seals on the injectors and once installed pressurize the fuel system a few times to check for leaks before you reinstall the rest of the intake. Also these injectors are slightly smaller than stock. This is mostly an improvement in fuel economy and idle smoothness, not power. Theres a lot of other 155 injectors out there that work just as well or better. NA volvo 850 (0280155746) injectors from 95-97 are virtually identical. Saab/Vectra V6 injectors (0280155712) make a nice upgrade at 21.5# if you decide to open up the intake a bit. Thats where I'll be going next. Ford Taurus 24v V6 injectors (0280155715) are even better at 22.5#.