Using sound isolating headphones as earplugs?

[Stanley Design]

I have wanted some Shure E(?)c's for a while, and I work in a machine factory. I like to protect my hearing so I'm one of the only ones that frequently wears the little yellow foam earplugs while I work. They work great. Most people I work with have a boombox in the area that they work and blare them over the machines. I want to listen to music too, but not interested in trying to turn up over everything and wear no protection.

Do any of you have experience using sound isolating in ear headphones in replacement of the little yellow things?

Also, E2, E3, E4, E5?

[TheCrack]

I do this with a pair of UltimateEars (model?). They are good on planes and subways, but I don't know how they would do competing with all the racket it sounds like you deal with. I even sleep with them in, but not playing sometimes.

I have to be careful with my hearing so I also got some great plugs for watching gigs - no lopping off the high end. They're pretty cheap too.

http://www.etymotic.com/ephp/er20.aspx