This part was designed to put a 1/4" neodymium magnet into a 1/3" diameter, 0.11" deep hole feature. The magnet grip is a little less powerful (since the magnets are farther apart from each other), but you also didn't glue yourself to the part. Engineering is tradeoffs.
I designed it for bainite's dice tower:
v.1 - http://www.thingiverse.com/thing:1044915 (fits great!)
v.2 - http://www.thingiverse.com/thing:1271858 (I haven't tested my part in this model)
but now I use it in my other things too!