At Cut2SizeMetals.com, we carry two different types of Aluminum Channel. Although the profiles are different (this is the shape as viewed from the end), these channels do share a number of things in common.
First, they are both extruded from 6000 series aluminum. This series of aluminum yields a harder material with good strength, but will crack if it is bent toward 90 degrees. Both also come in 25' lengths and are specified by the outer length of the leg and what is call the web, or thickness. In the photos to the right, you can see the profile of the channel in the shape of the letter "U". The uprights are called the legs, and we measure these on the outside. The horiztonal part is where we measure the thickness.
Why does it matter? As you can see from the top picture, American Standard channel has tapered legs, so the inside dimension between the legs gets smaller as you approach the bottom of the channel. And, unlike the Aluminum Association channel shown in the bottom picture, the thickness of the legs varies, and is different then the web thickness on the bottom.
Hopefully, you now have any easy choice. If you need straight legs, then you need the Aluminum Association channel. If you are looking for a tapered leg, choose American Standard channel.- Andy Hubbard