Using off the shelf C6 headrests in rear. I used the A6 because it is the only other Audi with Amaretto interior that I was aware of. Same anchor points/width. From more than a foot or two away, it's a close enough match to look pretty much stock.

The key difference is how it is cut away underneath in the curved shape. That lowers the headrest out of the rearward vision a lot. The height adjustment still works fine. In the pic. I think I have them reversed--height adjustment release button would be on the door side. Given their height, I can also get these in and out in seconds. I have the W12 adjustable four seater where there was enough clearance to just barely squeeze out the original stock ones. A more involved disassembly hassle as I understand it on the normal three across bench.

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Current #1: '06 D3 A8L W12 brilliant black w/ amaretto & 4 seat setup, GmbH custom, CPO; modestly VAG COM lowered, H&R 20mm rear DRA's with 275/35 on OEM polished + forged 20's; S8 sway bars (see: rear bar and gen'l D3 bar info and front bar); tweaked 385mm front factory brake mod and matching rear brake mod; matching C6 A6 back headrests (better rear view: headrest tweak); owner installed AMI retrofit with part number details here; other VAG COM tweaking to suit
Current #2. C5 '00 A6 4.2 ming blue w/ beige, new off showroom floor; Lemiwinks + VAG COM tweaks; smoked tails; RS 6 OEM 18's; RNS-D (CD) Navi
Prior: '96 C4 A6 2.8Q, still w/ family; '85 C3 5000S 5 sp FWD, '73 C1 100LS

helpful cross reference to a C6 post with MMI and other TSB's that also cover D3 A8's.