/HH looks almost identical to /NG except it's non-deliverable. I use Rithmic and DOM of /HHF1 (Jan contract) is empty for some reason. My broker is AMP. Is this tradable? I am specially interested in /NG-/HH spread trading. It looks constant range bounded with decent liquidity, which is ideal for spread trading. Has anyone familiar with this trading? I even cannot find margin requirement information either from CME or from my broker website....