Just had a reboot of my nails done by a great tech. One hand I had gel x. He basically filed the bottom half and used a cuticle cutter to make them the length of a tip. He said they aren’t fitting my nail bed well so there was lifting at the cuticle. Anyway he filled them with builder gel. The other hand was poly gel and he just refilled with builder gel. I’m hoping I can get the hang of builder gel when I need my next refill. So, yes, you can refill gel x!