I purchased 4 of these and had to dismantle my roll up doors to get to the bottom track. It turns out that I need 1/4" T-ends and these are 5/16ths. Trying to get a coherent response from customer service is difficult. They want me to send them a video of the issue, that I can easily describe in words and have done so three times! I want to exchange them for the correct T-end size or return them.
On a positive note, they appear to be well constructed and will servce the purpose with the correct T-end size.