SHANGHAI, May 18 (SMM) – Quotations for spot copper premiums were between positive RMB 200-250/mt in Shanghai in the morning business. Traded prices for standard-quality copper were between RMB 55,900-56,100/mt, and RMB 55,950-56,200/mt for high-quality copper. SHFE copper prices were volatile, but cargo-holders in spot markets stabilized their sale volumes and insisted on firm price quotes, still showing reluctance to move goods at the lows. Downstream producers stuck to the sidelines at prices above RMB 56,000/mt, but most transactions were made at above this price mark.