CONVENIENT LOCK --- The knob-style switch is 4 way rotary, you can easily rotate it to 4 modes with the arrow and icons to control your cat's access options: in only, out only, in and out freely, totally locked. IMPROVED WEATHER-PROOF BRUSH STRIP --- It provides a fixed groove with snap tabs for weather-proof brush strip, firmly fix the brush strip. Even if the brush strip comes off, easy to put it back into the fixed groove. This greatly help the brush strip reduce noise, stop rain drop, wind or pest like mosquito to the most. THOUGHTFUL SCREWS --- It comes with 2 packs of 8 screws each, one is packed with short screws, the other long. Please screw in with them from both sides to prevent crack out of incaution, don't just from one side. You could make 8 screws for the 4 screw holes with long + long, long + short, or short + short group according to the depth of door / wall being installed. EASY TO INSTALL --- Step by step installation instruction in the instruction manual included in sales box and installation presentation video for you reference, take care of notice and prepare necessary tools, easy to install as your need. The tunnel depth could be cut down according to your installation need. APPLICABLE FOR --- Inner size 2.17" / 5.5CM(D) x 6.18" / 15.7CM(W) x 6.30" / 16CM(H), it's suitable for cat with waist circumference shorter than 15.75" / 40CM. And the outer size is 2.17" / 5.5CM(D) x 7.56" / 19CM(W) x 8.46" / 21.5CM(H). It fits to being installed to interior doors, exterior doors, walls, windows, cupboards, glass, etc.