Hello,are you talking about actual replacement windows or just some type material to winterize you existing windows,I worked for a siding CO.and we did trailers that had the cheap reall thin windows,in it when we owned a double wide our windows were the real narroer indows didnt do a darn thing to hepk keep out cold nor cool in,.We hav a reall OLD trailer prob.196's and we got regualr replacement windows,to put in it the only prob those had such thin walls not like the new ones with 2 by 56 studs in so even though we got the narroest in depth they havd they stuck inside the home at least almost 3 in.so we litterally had to take 2 by 4's and build an inner window sill and window jam usiny 2 by 4's didnt look goos but no choice,you should be able to get a regular house window repalcement 1st you should try to find out what type of lumber ois in your walls if it was built from 2 by 4's or 2 by 6's and if you can open your window and try to measure from your inside of the window to the outside of your mobile home,to get an fairly accurate estamate how deep of a window you would need to fill your window cills,1 thing if you measure your window this way make sure to DEDUCT the thickness of the molding that goes around the inside of your window then how ever thich in depth from the face to your inside wall DEDUCT that amount from your measurement,what you will come up with and what you will nedd is fdoing this will give you almost the exact thickness of your walls and then you can order windows to that depth/Thickness of your walls now you may still find even though yopu order as small/dept window they sell that it's possible that the new windows will still stick inside your home and not flush what you will need to do then once you install them is measure from your inside wall to the front edge of the window that is comming into your home and then get at least 1/2 in.thicker to make new moldings for your windows,an extra 1/2 in thickness in the wood you use inside to make a new frame inside around your window,will give you the avility to take clear cilicone and put a bead around the inside of your new window frame to seal it tight and also you can put a bead around the outside of your frame as well this putting beads on the inside against the window and the outside against the wall around the edges of new framing,will totally seal your window,depending on your home it dosent have to be clear if the windows are white a white caulk should be used against the window to match the window around the frame and you can even put white on the outside of the frame too,esp if you plan to touch up the paint or repaint the room etc.when your dont,sometimes with the clear it's hard to get paint to stick to it for some reason,when you look for white caulk check the tube and make sure it says Paintable.you could check like a Lowes if they have them any big name lumber place windows to replace the old.make sure too it may be a bugger but try to take the inside molding off from around all windows you are going to replace and that way you can measure the exact sizes height /width that are in it now,and write each one down so you have a list of each window size as i said measure formm the inside face of inner window molding to the outside of your home and then deduct the thickness of the interior molding from that measurement and it sould give you the depth of the winows you will need other then measuring with molding off each window and writting it down after you measure as i said from inside to the outside deduct the molding depth it will give you the thickness of your walls and they will use this depth to order all windows,when you take molding off and there is a gap around the window (example a gap each side of a quarter inch ONLY Measure the actual metal windopw itself not the opening as you need a little gap as they should have if you use the measurements of the wood on the actual opening if your windows are ordered by that measurement their going to be almost to tight and a hrd time to install only measure the window itself not the actual openingas they should have space on top and sides so windows slide in to install them if yopu want after the new windows are in you could also put caulk around the new window before you put new interior molding this will cut even more air out too,a Lowes Lumber place or any big lumber place should have them .Jim