I got a set of these with my Rambler from Terratrike but they did not fit. Apparently they work for people UP TO a size 11 shoe and I am a size 12 wide. They make an extended size, which is on the way to me now. So, headsup to people with big feet and/or who might want to wear booties or something with these straps. Also, a suggestion to Terratrike to put this information on your website so people, like me, can simply order the right size in the first place.
I have 1 pair of shoes that almost fit but my feet become very fatigued when I use them. Luckily I could at least use them enough to see that they will be very useful when I have the correct size (i hope). The reason I bought them is I have lots of different shoes and plan to commute to work. I really thought about clipless and I still think about it. But, that was an expense I wasn't and still not ready to undertake. These power straps don't lock you in to a specific position so you have some room to adjust your foot to a comfortatble position, which was another reason I went with them. So if I sacrificed more power for comfort and versatility then I will just have to grow stronger