THANK YOU! Just buy one of those cups that fits on a nalgene bottle... basically no added space and minor added weight (especially if you go with Titanium).

You will be able to boil water quicker and safer! For an extra $6.50 and 150gm for the GSI Glacier Stainless Steel Bottle Mug or 130oz and $35 for the Vargo Titanium Mug which comes with a titanium cover!
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"Trust in God --and press-check. You cannot ignore danger and call it faith." -Duke