Items Used:

• Wire #1: USB Plug 3/8" x 1/4" (1/8" OD wire). This is the lower one in all the pictures below
• Wire #2 USB Plug 7/16" x 1/4" (3/32" OD wire). This is the upper one in all the pictures below
• 1/2" ID 2:1 Polyolefin Orange Heat Shrink 
• 1/2" ID 2:1 Polyolefin White Heat Shrink
• 5/16" ID 2:1 Shiny Clear Heat Shrink Tubing
• VT-1100 Heat Gun

Instructions:

1) Select the appropriate sized tubing for your application. Keep in mind, you have to get it over the connectors but you may want a snug fit on the wire.. In this example, we used 1/2" (Red) 2:1 heat shrink because the plug from wire #2 would not fit through any smaller tubing. 3:1 Polyolefin is a better choice if you want it to be more snug on the wire. Note, we used 3 different types/colors of heat shrink tubing in this illustration to show some different options. It's quite suitable for us to have used the same tubing (and color) for all three parts. If you're unsure, contact us for a recommendation

2) Cut a V-shaped hole in the tubing so the other wire can be pushed out. Place the tubing on the other wire once it's through the V hole. Shrink this one first as seen in Picture #3

3) Slide the wire back so that the shrunk heat shrink is inside the unshrunk heat shrink tube and shrink the second piece

4) For a better finished look, it's recommended you use another piece on top of the split like in the pictures below