Audioquest Banana Plug 4 Pack Gold. Suregrip 300, Gold Over Beryllium-

DIRECT-GOLD OVER BERYLLIUM-COPPER 

Beryllium-Copper is stronger, more conductive, and better sounding than normal phosphor-bronze connectors.
Direct-Gold Plating is optimized for sound. It looks dull because there is no underlying layer of shiny, distortion-causing nickel.
Cold-Weld System creates an ideal connection with better sound than solder. Slide the no-magnetic-interference ABS casing over the multi-spade, then slide both onto the conductor. Tighten Allen screws with a supplied tool to create a cold-weld connection between plug and conductor.