Genuine B&W ZZ28738 tweeter for 800 D3 series only. The D4 tweeters look similar, but will not fit. This was pulled from one of my 804's, I am the second owner. The original owner had this one next to a window and in the direct sunlight, so I'm guessing that's how the rubber started breaking down. It was like this when I purchased these in March 2021 and it has not worsened during my ownership (mine are not in the sun). 

That said, these work fine and I have not noticed any crackling or any other type of distortion or decreased quality of sound. I've attached a video to sample. When the D5's came out last week and they jacked the price up yet another $10k, I figured I might as well bite the bullet and just pay the $1000 for a new tweeter since I will not be upgrading anytime soon. You may recall the 804's with the continuum cone debuted at $9000 MSRP, then went up to $10,000 during covid, the D4's MSRP'd for $16k and now the D5's are $25k. Not sure why the extreme price hikes in such a short time when the drivers are all the same material from the D3 line, so I'll be sticking with mine for a while as I'm doubtful a small cabinet change is worth another 15-20k. 

You will need the special tool kit to install this; at a minimum a long 4mm allen key and their proprietary T-tool/extractor. I could rent mine out, but I'm not sure how I'd do that here. 

This sale is FINAL. No returns or refunds; the tweeter is sold as-is.