I've done MassDrop a few times and was satisfied with what I was receiving (Aurifil Thread) big spool kits. The shipping took forever.
Problem with this seam guide, is its the sticky type and invariably, the sticky fails. I have a Bernina and use foot 95. It's a 1/4" foot that comes with a seam guide that screws into the machine bed. I can flip it out of the way when sewing half square triangles, etc. If you don't have a Bernina, Thera magnetic ones. I'm really loving the idea of using Command Strips.