who makes those under the sub bass traps?

while surfing today, i came across these bass traps that go under the subwoofer. i could have sworn that it was rpg, or asc, but i now i can't find them. could anyone provide a link? there were 17", 20" and another larger model. i'll send a copy of "heavy weather" to the first one who can help me out. while i'm at it, anyone have
any feedback about the effectiveness of these vs. conventional tube traps (echobuster, asc, etc.)?

aloha keith