What is "zhongruan"

The zhongruan , is a Chinese plucked string instrument. The zhongruan has a straight neck with 24 frets on the fingerboard and 4 strings. It is usually played with a plectrum (guitar pick). It can also be played with fingers (index finger and thumb with acrylic nails), which is similar to the way of playing the pipa (琵琶). The zhongruan is a tenor-ranged instrument in the family of ruan (阮). In ancient China, the ruan was called Qin pipa (Qin [Dynasty] pipa, 秦琵琶) or Ruan xian (阮咸). Now the ruan has expanded to different sizes and the zhongruan is the "medium" one.