Wanted to put on a strap I have had laying around for 5 years onto my I4's. I read through Demok's how to and decided to do a write up with pictures, I'm a visual person. This is my first write up/walk through. Hope it helps.
This only took me about 5-10 mins including taking the pictures to do the dis assembly, strap install, and re assembly.
Things you will need:
-Second strap of choice
-Needle nose pliers
-Flat head screw driver
1:First thing to do is remove the lens and then the ear and strap assembly.
If you know how to do this you can skip to step #2.
At the end of the strap is a small tab on each side. Depress the tab and push towards the front of the mask(lens). the strap bracket will slide forward.
Next is to remove the lens. pulling the soft ears in towards the center of the mask you can see a rounded corner of the lens. Pushing gently in each wide the lens will slide forward and you can then remove it fully and set it aside.
2: Once the lens is out you need to remove the strap assembly from the frame. The two strap brackets come out by tilting the top back and the top guide post clearing the guideway. You may have to pull some but it will slide out. Repeat the same for the other side.
3: With the strap assembly removed time to pull out the screwdriver. You need to remove the soft ears that are retained by a screw. The piece the screw goes into will fall out when the screw is removed so make sure to grab it and set them both safely aside.
4: It is now time to install the new strap. I found it easiest to with one hand pull the stock strap down to stretch it out of the way and make more room for the new strap to slide in. Start with one corner, I did not need to use anything to push it through some but you may need to encourage it with the screwdriver. Once it is sticking out some pull it all the way through with the pliers.