SHANGHAI, May 13 (SMM) – Spot copper in Shanghai was offered at a premium of RMB 30-120/mt over SHFE 1305 copper contract on Monday. Traded prices for standard-quality copper were between RMB 53,820-53,890/mt, and RMB 53,880-53,980/mt for high-quality copper. SHFE 1309 copper contract extended gains, leaving little room for arbitrage. Spot copper supply decreased, pushing premium up slightly. However, spot copper premium then narrowed as buyers showed low acceptance toward higher prices. Prices of hydrometallurgy and standard-quality copper remained firm due to tight supply. Cargo holders largely held offers firm as price gap among SHFE copper contracts narrowed and as copper price trend is unclear. Middlemen held off from buying high-quality copper at premium of RMB 100/mt, while downstream producers purchased on an as-needed basis.