Claim: The Zhongruan is made without the use of any plastic or ivory with pegs made out of the same material.
Evidence: It is usually made of plastic, buffalo bone or ivory. 
The frets are usually made of plastic, buffalo bone, wood and metal (copper). 
For a good quality zhongruan, the frets are made of a combination of plastic and copper, or wood and copper, with the metal part inlaid at the top of each fret.