Wanted to share my experience as I went through a lot to get this done and finally have success.
First, I had a lot of issues because I had cut a full sim (DIRECTSIM4G-D) all the way down from an activated droid bionic. This got me service, but not LTE. This took a lot of troubleshooting to figure out since even cut down it was getting LTE in the bionic via an adapter. BTW, I cut down using a Noosy sim cutter & adapters, I recommend the cutter highly, but in retrospect I wish I'd never bought it as this isn't what ultimately got me all set up.
Second, the Sim that they'd have you use (if they carried this) is actually DFILL4FF-NFC-A - which is what the moto x takes. Luckily my wife got a 2014 moto x and I was able to activate in hers, then shift it over, now everything is perfect.
From other people's experience, I think a DFILLSIM4FF-A, or BULKSIM4FF-A will work if you can get it activate in another device first. Don't bank on it though. I had to use DFILL4FF-NFC-A I think simply because they would not let me activate a BULKSIM4FF-A in the wife's moto x even though that IS an nano sim, kinda crazy.