I have a vintage Premier bass drum that is 21.5" in diameter. Remo can make custom heads for it, but the price is too high to allow for any experimentation. Right now I have two sets of heads, the original calf and a set of Fiberskyn 3's that I got 20 years ago. They are nice, but ring too much for micing even when I use the drum's tone controls and felt strips. I can get it close with a pillow, but it is a hassle to constantly be messing with it.
I have a another modern kit with a Remo muffle ring in the 22" and it sounds exactly like what I am shooting for. So I ordered one from Portsmouth Drum Center. The ring was oversize for the drum, but it was simple to cut a 1 1/2" section out of the tray and the foam to get it to fit.
I put it under the batter head, did a quick tune and the drum sounds like it never did before with exactly the low fundamental thump that I had been seeking for way too long. It might be my imagination, but the drum sounds a bit louder with the ring muffling it than when I used the pillow. It sounds really good, especially in the smaller rooms I sometimes play in where I can't run it through the PA with a bunch of EQ.
All in all, not a lot of money very well spent.