Used some random, untagged, yarn from my stash - pretty sure it’s Red Heart. I also added one more row (so row 17 with the loop became just another row, and row 18 had the loop) because it only came half-way up the mug I tested it on. Oh, and I also chained, I think, 20 for the loop. I’m not sure, I just chained until it was easy to fit over the button. I would advise not fastening off until you’re sure that your loop is going to work for you.