I have the 425s, which is the model below, but only the insides are different, so I can answer your question. Sound isolation is very good, but it depends on t

I have the 425s, which is the model below, but only the insides are different, so I can answer your question. Sound isolation is very good, but it depends on the tips being the right size for your ear canal. Some only swear by the silicone ones, others by the foams. Note that it's a lot like wearing earplugs, so you'll hear your steps if you have harder soles, etc. Personally, I've always used the foams, I found them more comfortable and good enough for my needs. The silicone ones wouldn't hold well or were too uncomfortable. However, when it was time to change them, I bought a set of Comply tips and isolation was much better. They're a bit longer, so you shouldn't buy too many at first before you check whether they bother you. They're also somewhat more rigid, so you have to hold them in a bit longer while they expand, so they're not very practical if you need to put take them out and put them back in often.