None that I can think of.

Used with the pyramid cones, those things takes things to the next level. You might find them a little pricey at first until you screw them on.

The improvement you get is amazing. More spaciousness between instruments, more improved image height, decay of voices and instruments becomes more apparent. Bass notes improve with better tempo that will make your feet tap. I can go on and on........

Highly recommended!

Negatives:1.) The screw often gets mangled, or does not fit into the threaded insert of either the Those Thing, or the Pyramid Cone.
2.) Only available in black
3.) Not as effective as The Shelf, which is, of course, much more expensive.
4.) Components will slide around.
5.) The worst, most confusing product name in the business.

For heaven's sake, this should be the last tweak you do for your component(s). Start off with a set of cones. Then find a good cone cup [I have found BDR's The Pits mk. 4 to be the best]. Then add a weight, such as Bright Star's Little Rock, the Shakti Stone, or VPI's Magic Brick. And then, you can experiment with Those Things.

If your component runs hot, then you will want to choose Those Things over The Shelf. Otherwise, if you can accomodate it, save your money, and get The Shelf (I only have brief exposure to The Shelf. But from what I heard, it just might be a five-star product. Stay tuned (no pun intended). Those Things add a bit of refinement to the sound. I notice that image outlines are sharper, so there is now less confusion. That also means more space between those images. Which leads to greater see-through transparency. The timing of the music is better portrayed. The start, stop, and decay of notes are unambiguous. More detail is now available. Others who have used the Pyramid Cones and The Pits by themselves have remarked that the sound can be a little hard, clinical, and choppy. I concur. But, if you also add Those Things, these characteristics tend to subside.

90% of you have rooms/systems with too much upper and midbass. ASC Tube Traps and other room treatments are effective. But what if you don't have room to put up such objects? Well, even if you do have room for Tube Traps, BDR's Those Things further minimize that bass boom. This reveals details in deep bass, that you never thought existed. Wait 'til you hear true bass, not that muddy boom that you all are infatuated with. You will hear fingers on strings, feet on pedals, and tympani rolls that shudder with visceral force. I brought out all my rock/metal albums, and I discovered how sinewy the bass guitar could be. And when I brought out the Erasure, New Order, and La Bouche, I finally heard the FLAVOR of each synthesizer.

Unless you have a BIG room, do not bother with any of BDR's mk. 3 stuff. The mk. 3 stuff only exacerbates the colorations. The mk. 4, however, is the complete opposite. The mk. 4 products will get you another step closer to reality. And that's what were striving for. Leave your colorations behind, and pick up the mk. 4 versions of the Pyramid Cones, The Pits, and Those Things.

Again, if you need better ventilation, or simply cannot afford The Shelf, use Those Things mk. 4 as the finishing touch. $150 might be expensive in absolute terms, but compared to all the other $$$$ waste-of-money band-aids out there, Those Things really work. As a system, I highly recommend BDR's mk.4 stuff.