Circular knit is made with a machine that knits the fabric in a continuous circle (tube); the weight is “light.” The fabric is thin. T-shirt fabric is the best example of circular knit fabric.
Circular knit fabric has a gauge of 12 to 22. The higher the gauge is, the thinner the fabric.
Flat knit is made with a machine that knits the fabric in sheets (or flat) and the gauge is 2 to 10.
Flat knit is thick sweater fabric like your grandma makes sitting in a rocking chair with two needle-sticks.
Thai Son S.P works with circular knit fabrics like Single Jersey, Interlock, Pique, Rib, Ponte Roma to name a few.
When talking about Knitwear it is important to clarify which type of knitwear you are talking about: circular or flat because they are significantly different. Many people confuse the two.