3mm felt tape. 1/2" width. i kinda wish i would have used one continuous piece and molded it around the screw pillars. i think it could fully seal if i did that but getting it just right could take a long time.
and for anyone wondering the best way to put felt in to tame the highs. just cut to just under the inside of the pad adapter screws and tighten the felt up behind the pad adapter and it’ll never move and looks cleaner than stock imo.
just played around with a tone generator for a minute and the 11-35hz bass region is substantially improved. 21hz has a serious rumble now. they rumble! not like distortion rumble, but good rumble. didn’t think these lil guys had it in 'em.