Prim is an economical steel-core string made in Sweden. Tension is indicated by the color at the ball end of the string. Light is blue, medium is green, heavy or “orchestra” is wine. The pitch is indicated by color at the peg end. The G and C have very good sound for the price on many cellos, and are our go-to string on budget cellos. It allows us to splurge on the A and D by other makers to get a quality sound at a lower price.