Sizing really has to do with how much fluence I want to get out of the mat. The bigger the mat even though the temperature doesn't change the fluence is higher. After that I decide if I want to have single or full spectrum Biomat sessions. With a big mat like the Single size, it only has one temperature control unlike the queen that you can lay on one half turned up high and the other half turned up low and sandwich myself in between.
Sandwiched inside the Biomat Queen, I call it the Biomat burrito. There is very little heat escape. My 2nd best option for doing a full spectrum session is getting the professional size Biomat and the Mini and using them in a similar way. I HAVE MY FAN ALWAYS HANDY SO I DON'T RAISE MY CORE TEMPERATURE PAST WHAT I WANT IT AT.
Some people only have a target area to work on and they might like the Biomat Biobelt. It is the smallest size but some people put it on their stomachs who learn to build 3 to 5 lbs of aerobic bacteria in their gut. When the aggressive probiotics from some brands get really warm they can grow quicker in the gut and colonize quicker. The Biobelt won't raise the body core 3 degrees. Many people lay on a professional size Biomat and use the Biobelt on the highest level for a full spectrum spot session.
The Biomat professional is the most popular size people get. For beginners who can't stay on as long and can take a long time to work up to keeping the core temperature 2 to 3 degrees for long times, the Single size can be too intense for many beginners. It does come with a cloth cover but for the time when people can handle laying on their urethane cover without the fabric and put a waterproof cover on it, it's there for people months or years later when they can handle it. Not everyone can go to the beach and lay down on the super hot sand. It's kinda like that.
...because no one gave me advice after I bought my first Biomat