Are you tightening the cone caps onto the bases in the kit or onto existing fittings on your vehicle?

I used new 1/8" copper tubing with original-style 1/8" threaded sleeve nuts from NAPA (WH 6100X2 Weatherhead-Eaton) .

http://www.napaonline.com/Search/Detail.aspx?R=WH_6100X2_0214480248