When H&K reworked the SA80 rifle in the early 2000s, they also improved many of the accessories that went with it such as the magazines and the blank firing adaptors. The original blank firing adaptor was a cage that went over the muzzle of the rifle, with a thin spindle that passed down the barrel and helped increase the pressure form the blank round to cycle the action. This rod screwed in, but needed a rod or Allen key to tighten the rod down. H&K left the cage part of the adaptor as it was, but replaced the thin rod with a much chunkier part, with a cone shaped end to it:

The end of this piece was also modified, with a large tightening handle with serrations for grip that allowed the blank fire adaptor to be attached by hand without the need for any specialist tools:

The other end of the adaptor has a cut out to allow it to be fitted around the barrel, and the whole of the adaptor has been painted bright yellow to make it very obvious to exercise staff that the troops are indeed using blank ammunition and not live:

Should live ammunition be loaded by accident for whatever reason, the adaptor is designed to be able to absorb the round without harm to the firer or other people on the exercise. These blank firing adaptors get a lot of use and punishment, so they are often extremely worn, like this one, with much of the yellow paint missing. Whilst very effective at making the weapon cycle with blank ammunition, there is a downside as ARRSEpedia explains:

Due to most of the gas being trapped within the barrel and working parts of the weapon, it tends to get absolutely goppin’ real fast. An absolute pain in the arrse after you’ve just been the fire support section for the Platoon-level attack, fired off loads of rounds and got back to the harbour, only to find the working parts have more carbon on them than burnt toast. Then you have to spend most of your admin time scraping all the crap off when you could be catching some zeds in your gonk bag. Happy days.