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How to apply the back glass camera lens to the phone?
First, use the Wet and dry Wipes to clean the camera, then put the adhesive tape to the phone, then put the back glass camera lens to the adhesive tape. If there are any dust is the glass lens, you can Dust-absorber to clean it.
This camera glass lens fits for LG K40 .

Package include:2 X glass camera lens, 2 X Wet/Dry Wipes, 2 X Dust Dust-absorber and Installation and Use Guidance