On the London Metal Exchange, a Ring is a five-minute period during which one specified metal is traded on the floor of the exchange. The Official Kerbs are the specified times during which, after the morning and afternoon rings have finished, several or all of the metals are traded simultaneously on the floor of the exchange.A screen-based trading system operates alongside the floor-based trading. While spreads maybe tighter, and the markets more liquid, during the Ring, it is normally possible to trade any metal whether it is in the
Ring or not.