An S318 & an S318 are very similar - an S250 is 86 7/8" LOA X 79 5/16" wide, while an S318 is 77" LOA X 70 1/2" wide. That's why the 318 fits an M37, and the 250 sticks out. The photos of my S250 were a little challenging - I have a kid changing apartments, and the garage is fuller than normal. Note the patch on the front roadside corner - the shelter was harpooned by a forklift before I got it, but Good 'Ol TB-43-0124 showed the approved repair. The power inlet has been upgraded to a newer style Pyle-National, and the old heater inlet / exhaust have been modified to cable pass-throughs. The side exhaust has been reconnected directly to a 24 VDC blower. The old side antenna feed through has been blanked off. I am now building light fixtures since the original fixtures are not too good for what I need, and air conditioning may be added as well. Unfortunately, the military AC I tracked down for the shelter may be too noisy for what I need, so I may have to build my own. As you can see from the second photo, mine was also used for an AN/GRC-122 as well.