This is fitting that we have designed and machined since the Nissan Power Steering Racks have extra long threads before it reaches the internal O-Ring seal. If you buy other fittings lower o-ring fittings similar to this, the hex bottoms out before the O-Ring can seat inside the rack. This is designed to work perfectly with all 240sx and Silvia chassis (S13, S14, and S15) as well as 350z/G35 chassis.