Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: Will this AC fill a 40 inch window opening with side panels fully extended?
Document: So far this ac is a great one! I have a 6000 btu in the living room and put this in the dining room as it's all open and the one just did not get it cool enough into the kitchen and dining rm also. ...about 33 sq ft total and it's nice and cool in here now. It's pretty quiet thankfully and was small enough for me to fit into  that smaller window opening wo the side panels.
I was a bit wary of this AC unit since i had never heard of SPT. The unit seems well constructed and is surprisingly quiet when the compressor turns on. It's 6000 BTUs work well at cooling my bedroom and the various functions work well. The temp setting works well, cooling my bedroom within a degree or two of the set temp. (i have a thermometer in my bedroom)The flexible side window extensions appear to be fairly good quality plastic as well. I would definitely recommend.
I bougth a SPT 6000 btu window AC unit it works grate then I bougth a Igloo RCA 8000 btu AC unit I figured since it's a larger unit it should cool better, wrong I put the SPT unit back in the window it greatly out preforms the Igloo 8000 btu. I was going to give the SPT 6000 btu to my half sister but now i'll keep the SPT 6000 btu ac unit, and give her the Igloo RCA 8000 btu ac unit instead.
I got this AC last spring and its been great. Very heavy but it still was manageable for a 5'3 female to carry up three flights of stairs. Relatively quiet with simple settings and handy remote. I highly recommend! !
We are in Hawaii and this air conditioner is great for drying out the house . Our home is very small so it works great. FYI we put it in a little crooked so it drains outside properly we put it in the wall instead of the window. We love it!
I am on my second summer of using this window unit, and thank goodness I have it or I'd probably melt. I have this installed in my bedroom and use it to keep cool at night. However, during the day I leave my bedroom door open and it helps to cool down my entire apartment.
I was looking for a window unit narrower than 16 inches. This product is listed at 15.75 inches. I just put a tape measure on it without taking it out of the box. It is exactly 16 inches wide. I am not sure what to do because if I try to install it and it doesn't fit, it might get scratches on the sides. Don't need a hassle returning it.
We have 2 other LG A/Cs and purchased a third. But when it arrived completely defective and we had to send it back, I decided to see what else was out there. SPT was a brand I never heard of, but with such great reviews from here and Home Depot, I decided to give it a chance. It is so much smaller (width wise) than a typical window A/C, but is just as (if not more) powerful.
This unit was purchased for a 12 x 13 foot spare bedroom. The unit fit perfectly into the window and cools the room quickly. The thermometer on the unit works well and keeps close to a steady temperature. The remote control is handy. The written instructions on how to install the unit could have been a little better but we were still able to figure out how to install it properly. Overall very good purchase.
I'd rather pay 80 bucks less since it's for a guest bedroom, but since it can get VERY hot here, I need performance.... Hope this info is helpful to those who need the smallest unit they can find. UPDATE: I shoved it into place and it's in the window. I find the unit to be unhelpfully loud. I am using it in the "dry" mode because of the humidity we are experiencing. I'm personally disappointed that I spent this much on this unit.
Answer: The maximum is 36 inches. You will need to use some material to cover the extra 4 inches.