A true sperm plug is to stop other males from mating with the same female.. the male does his deed, inserts a SPERM PLUG and blocks the passege. This stops other males from breading sussecfully with that female and garenties the survival of HIS genes. but since you can bread more then 1 male with the same female with ball pythons that theary doesn't apply. I understood that there is a "plug" on ball's but that is only a peice of shed that comes off when they are ready to bread. I may be WAY OFF, I'm a begining breader my self with only 1 clutch under my belt, but I do alot of research online. Since I see so many adds from known breaders talking about selling there males that are producing sperm plugs I thought I'd look it up. the info mentioned above is what I found. I'll post a link if I can find the articals again.