No, you've got to do some cutting and fitting. The main cap is modified.
Thx for the info. That's fine with me and can just move the cap from MWC to MWC. I have three, but have replaced most of my lesser water containers with Scepter's 'civilian' version 20L, the 'Fat Bottomed Girl' as I think of that series of 20L. Both gas and water have the same small cap and the water pour spout fits on the gas jugs (shhhh don't tell the EPA / CARB). The civilian series jugs are about 2/3 as thick as the milspec, by weight. Same roto-mold process. At about $19 for the water and $24 for the gas they are a great bargain for a sturdy jug, as long as you don't have to fit them in a NATO-spec carrier / rack.
This pic's about 18mos old, I've since replaced several more of those CARB-spouted abominations with the red scepter civilian jugs. Need to take a fresh pic.
eta the fuel and the other color (diesel yellow and the blue works for either water or kerosine) 20L 'civilian' jugs are the same jug and same ratchet-latching outer cap. The yellow inner spouts are different for gas or water. And CHECK THE SPOUT BEFORE PURCHASING IN A STORE, people like to swap them, you might find a crappy gas spout in your water jug.
I'll take a couple example pics tomorrow, if the rain lets up enough.
The only downside is that unlike the milspec containers the handles are identical, can't tell the difference in the dark, and it isn't as easy to carry two empties with one hand like you can with the MFC. I've been considering wrapping some cordage around the gas can handle so a person can tell by touch. Not that it really matters, there's only a couple very improbable scenarios I can imagine where such a thing would be needed in the dark.