The dB killers are the inserts that fit in the outlets of the pipes. You can just see them fitted in this pic. of my bike. They are held in place by a little bolt under the end cap.



The discs are extra noise killers that fit at the pipe end of the silencer and help lower the noise even more. My Leos for my Tenere didn't come with the discs but the pair that I bought for my Caponord did. The Capo isn't too noisy without the discs so I fitted the discs to the Tenere instead as I found it a bit too noisy. They have done the job well and for me the noise level with the discs and the dB killers is just right.