I purchased the 6" x 8' hose to install on my portable air conditioner. Anyone that has one, you know the heat that radiates from the included hose is very high and inefficient. Although this hose does not look the prettiest, it is an absolute must for replacing the included hose on your conditioner. Running my air conditioner prior to this hose, I could only keep the room about 8 degrees below outside temps. After installing this hose, the room cools MUCH FASTER, and also gets about another 6 degrees cooler compared to the outside. An almost double cooling efficiency. This hose is room temp to touch, and feels like it contains >90% of the heat my previous hose allowed through. In addition, the air conditioner unit runs much quieter due to the sound insulation this hose provides. At least 30% of the noise from your AC is coming from the turbulent air flow rattling around inside the hard crimps of your standard plastic hose.
If you do purchase this hose for your AC, make sure to get a size slightly larger than the diameter of your input/output, so you can fix the hose to the exterior of the couplings with a good duct tape. Honestly, if you try to fix the hose to the interior, it seems like you might end up rupturing the lining and exposing the fiberglass inside, which would be bad. I used the larger size and it secures nicely in place with a good 3" wide duct tape.