SHANGHAI, Apr 21 (SMM) - The mainstream transaction prices of monocrystalline silicon wafer M10 and G12 stood at 6.44 yuan/piece and 8.07 yuan/piece respectively as of April 20. The prices of silicon wafers dropped slightly as the shipments of high-priced goods were sluggish. Although many silicon wafer companies such as Zhonghuan held their prices firm at 6.4 yuan/piece, the actual transaction prices dropped to 6.38 yuan/piece. The silicon wafer prices may decline still amid the falling polysilicon prices.