25$ shipped in the US, 35$ anywhere else, measure the center to center dimension of your extensions and round down to the nearest 5mm, thats the size you'll want. all of them have the 1/8th turn mount so it'll work with the edge or a 310/910xt with the quick release.

edit: final inventory, im not going to make anymore so this is it.

4 80mm mounts
1 85mm
2 100mm
and 1 110mm





the edge will mount a little tighter than the 310xt due to the quick release plate


mine is actually only set up for the 310xt, thats why it looks a little different. mine would be a 1/4 turn. the other 2 are 1/8 turn to accommodate both the edge and the 310xt