http://www.earsound.com/shurefit.asp Make awesome custom fit earbuds for about $130. These cost £8. Sugru is a moldable silicon that sets permanently, similar to PlayDoh but doesn't go all crumbly when dry.

This instructable gives you advice on how to make your own safely, either for use with headphones or as earplug for sleeping.

DISCLAIMER
This instructable involves jamming stuff in your ears and is not suitable for anyone. you'll probably get it stuck and have to spend hours in A&E. I hold no responsibility if you continue following this instructable and result in said situation.

That being said, read on.

Step 1: What You Need.

-Sugru, 2X5 gram pack
   -making the perfect fit earbuds
-Cheap rubbish headphones (preferably in-ear)
   -doesn't matter how low quality
-Cotton earsticks
   - cleaning and moulding
-Tissue
   -stop you pulling out your eardums

Step 2: Prep

Wash your hands and clean those damn ears! You wanna get as clean a cut as possible with the Sugru and it's gonna be easier to get out, cotton bud those things free of any dirt you may have been saving for a rainy day.

Step 3: Protect/Damage Your Eardrums

This part is a bit risky. In order to stop the Sugru flowing into your brain it's advisable to jam something not sticky in there before hand, fold up a small piece of tissue (about 3cm square) till it's about 5mm square and push it into your ear canal till your hearing goes. This will need to be extracted later so not too far otherwise tweezers and an assistant will be needed.

Step 4: SUGRU!!

Now it's earbud time. It's best to do this one ear at a time incase you get a reaction. That way you don't go to A&E completely deaf.
Take a 5 gram piece, half it, roll it into a dull point (like picture) and insert into ear. Push in and around securing all gaps, a good fit will close off almost all sound from around you.

At this point if you're missing out the headphones and just making earplugs to block out sound skip the next stage.

Step 5: Headphones

Take your cheap headphones, take off the rubber protectors and jam in your ear aswell, you need to angle them towards and into your canal so they follow the thickest part of the mold. May be easier to understand when you see the final model.

Leave your assembled mess in your ears and find something to do for about half an hour, you want it to be very lightly set.

Step 6: Remove All Hair

Should have mentioned earlier but assume people read through before following, if you have hairy ears this bit will hurt. To take out the mold you have to be very careful, it's gonna take a few days for the Sugru to properly set but after about half an hour of sitting in near silence you can carefully edge out the ear bud. to do this rather than pulling on the cord it's a good idea to pull the ear all around to loosen the outer grip, pull on your earlobe and gently massage around the area and slowly and gently edge the mold out, do not rush this bit or you'll squidge it and have to start again.

If done sucessfully you should have something resembling the picture.

Step 7: All Out

Essential now you've removed your mold to get out the tissue you've jammed down there' mine went too far so had to use tweezers, a good reason to have someone around to help you here cause this took a while after pushing a little too far. Also give the ears a good clean with water to get off any traces of Sugru and get someone to have a look to make sure there's nothing left.

Step 8: Pokin' 'Oles

To make sound come out you need to have lined up your ear canal with the direction of the headphone and made a hole for which the sound to enter your brain, this can be a bit tricky because people have ears blocking the path way so about a 110 degree angle will be what you are aiming for. Snip off a cotton bud head and run it down the centre of the ear canal in the Sugru (see picture). Again be very gentle as you don't want to alter the mold.

Once the hole is in place add a little more Sugru around the earbuds to hold them in place and leave the whole lot to set for a day or two.

Step 9: Fin

Let the Sugru cure for a day or two and you'll have a comfortable, self fitting set of earphones. Listen to music on the underground without having to blow your headphones at full volume.

Or cut out the headphones and steps 5 and 8 and you've got a perfect fitting pair of earplugs for a comfortable nights sleep.