When my Keurig K2 Duo needed to be descaled a number of months ago I was able to handle it with a 1:1 vinegar to water solution. But when it needed to be descaled 2 weeks ago vinegar-water fix didn’t fix it. I was disappointed but hesitated to call Keurig because I was sure they’d ask if I’d tried their descaling solution. So I ordered it. It arrived a couple of days later and I followed the instructions to the letter. It WORKED. I’m on a 3-month automatic replenishment schedule. As well as vinegar and water has worked with other coffeemakers, I’m going to use the 3-month brewer care kit from now on.