Each set is individually tested and flow balanced in-house to within a 1-2% variance. The results are included in your custom flow report that accompanies every set of DW injectors. Our flow report also includes additional set-specific data useful for tuning. DW STi injectors also feature... 100% drop-in fitment OEM 12-orifice atomization plate (4-hole for 550's and 650's) upper and lower o-rings 12-month comprehensive warranty