If you have an H&R muzzleloder it is a necessity to get the mu plug if you want to shoot bh209. With any muzzleloader, you will need a 209 breech plug and and it has to be a sealed one. If you go to there website, it explains more about it www.blackhorn209.com There are a lot of good points to the mu plug even if you do not want to shoot bh209. As far as I am concerned, it is a great upgrade for the H&R muzzleloader. I hav ebeen shooting ot since last spring and I have not had one ignition problem with bh 209 in any of my inlines.