I tried single and dual Amstel aiders and did not care for them. They are difficult to find with your foot when descending, especially in the dark. They are light and flimsy and move quite easily. You can easily push them out of place with your boot and their is not enough material there to make a decent, open target.
After reading a bunch of reviews, I purchased Backwoods Mobile Gear GC-One 3-step aider. It seems to work much better than the Amsteel as they have enough weight and firmness to hang straight down and retain their open shape. Backwood Mobile Gear or the EWO UltimAider are the way to go.