These clamps are compatible with the aerobars for the first-generation Trek Speed Concept 9-series (model years 2009 through 2013), and also compatible with the 2012 Bontrager RXL aerobar, which uses the same clamping hardware.
The clamps significantly clean up the front-end hardware of the Speed Concept or Bontrager RXL aerobar, reduce the bolt count from 14 to 4, and drop over 200 grams of weight in the process. Read the whole scoop here. Each clamp starts as a one-pound block of 7075-grade aluminum (stronger than the cheaper 6061 on stock parts). They're CNC machined down to just 26 grams each, then black anodized. They will accept any standard aftermarket extension. The optional top caps shown in the video are available if desired. You must use at least 5mm of spacers beneath these clamps (some Speed Concept bars have a 5mm spacer bonded to the bar already).
A note about the top caps: as shown in the video, their intended use is to be sandwiched between the clamps and your arm cups. They are NOT REQUIRED, and the clamps will work just fine without them.