The wires installed onto my NGK CR5 resistor caps just fine. Bike ran smoother after install (I run an Ignitech programmable ignition which can't get enough EMI protection). However the coil ends were not pre-assembled as advertised and they are VERY stingy with the wire the provide. My Ducati is an L twin and the path from plug to coil is long... I had enough wire with zero to spare and could not have afforded a single mistake so measure 3 times before cutting. Technically I did not have enough wire and would have preferred to route them differently to avoid stress at either end and also show off the wires a bit so I could do neither. So it's a nice product and reasonably priced but I'm still disappointed.