Sugru starts out slightly sticky, like Silly Putty, but after a few hours solidifies into a harder rubbery texture which retains its shape but is still pliable. It can be used to fix any variety of things, or to "hack things better" as the Sugru motto suggests.
This instructible details how to fix the silicone rings on the earbud headphones that come with the Apple iPhone.
Step 1: Start With Broken Earbuds
The rubber rings on both sides was separating from the plastic. That's bad, because obviously it looks bad, but also because the lack of ring leaves a slight sharp edge on the surface which was beginning to irritate the inside of my ears.
Additionally, one side of the earbuds was coming apart, the two plastic parts no longer glued together.
You can see what remains of the rubber from one side in the photo.
Step 2: Get Some Sugru
Each packet contains one of four colors, black, orange, green, or blue.
A single packet has far more Sugru than needed for this repair, so I did my best to seal up the rest of it to use for something else.
Step 3: Make a Sugru "worm" and Wrap the Earbud
Note: Although the Sugru people say it's safe for your skin, I have sensitive skin, so I wore food-handling gloves for this step.
If you want a clean-looking repair, it's important to get the worm as uniform as possible - it should be one thickness its entire length, with no bulges.
Stick one end on the seam of the repair. Do not crush the worm yet!
Slowly and carefully stick the rest of the worm along the seam of the repair.
Some of the worm will be left over. If there is no worm left over... start over with a longer worm.
Step 4: Cut Sugru Worm to Length
Step 5: Smooth Sugru to Desired Contour
Because the Sugru is so pliable, it's easy to mess up in this step and make an uneven repair.
Let the finished repair sit for a few hours. The Sugru will solidify and lose its tackiness.
Within 24 hours your part should be safe to use without deforming the repair.