PVA at the back of the UM3 is problematic when printing anything longer than 12hrs (maybe less) so I wanted to use a Polybox (I did create my own box from a rice storage but it doesnt look at nice as the polybox, just a matter of preference I guess). However I want to retain the NFC reader for ease of use. I printed this in CPE+ black and the tolerance is a bit loose. I also printed in PLA grey and that has a better fit. ABS would be a friction fit without scaling model and letting it shrink a bit.