The main issue I have found with Pigtails is on the Female end. On a few of them, the conductor (round metal piece in the hole) is too far down in the plastic and does not make contact with the male prong when they are screwed together. I had some from Ray like that early on, but his QC has gotten better over time. Now I look them all over before starting any assembly and have had no unexpected problems. I have only ever had one that just did not have continuity on one of the conductors.