There are discussions of which ferrofluid to use, as the original is apparently NLA. I used the Ferrotec (Kef OEM) universal fluid sold through Parts Express. The anorak set will undoubtedly shiver at the notion, but they sound good and it'd be easy to swap in future. Having recapped 2 pairs with Falcon matched caps I don't think I'd recommend. Not hard, especially if you've already got the speakers disassembled, but I didn't notice any real difference that would justify the cost.