All of the towels I use are the culmination of many years of trial and error. As I'm sure you know, microfiber towels aren't cheap. I'd be ashamed if I actually added up how much I have spent to get to this point. I know I can save you a lot of time, energy, and money by giving you access to buy exactly what I'm using on my cars.
Although you can use this towel for a ton of stuff, the main purpose is to use with a drying aid. I primarily use Bead Maker, but Optimum Car Wax or CarPro ECH2O are good choices as well. Since drying is the step that has greater odds of scratching than most, I segregate these towels and only use for drying. I've found the weight, size, pile all work very well as a drying towel.
Number I have in my cabinet: 20.
Note: Since I buy in such volume, I'm able to get all of us better pricing than you'd get on your own. I sell these towels at the same price that you would pay if you bought them in bulk 25+.
420 GSM: This is the weight per square meter of material. The weight does not necessarily mean the thickness.