Easy to install! Great Blinds! Lets in little light. 

If your window is a 36 get 36. If its 36.5 get 36. If its 35.8 get 35. Theres little wiggle room. The window in the picture is 31 and the blind is 31. Perfect fit. My other windows were 31.5 so the I had to screw in the top of the frame not the sides cause theyll fall out. 

Pro tip. MEASURE!!!, Maybe just buy one blind. Test it out then buy the rest. Thats what I did.