My Grados are pretty comfortable. They are an on-ear style that uses a full foam ear piece and I can wear them a couple of hours without them bugging me. The outside of the drivers are plastic but the build quality is good. Not like their really top end models that have wood over the drivers, but certainly acceptable. Replacement foam ear pieces are readily available from Grado to maintain comfort and should they get dirty.
A couple of things to note. Since these Grados are not an over-the-ear style others can hear what you are listening to and you will be able to hear (depending on how loud you listen) sounds around you. The other is that while you can get an 1/8" plug adapter to use with an mp3 player the Grados drain the battery pretty quick.
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AvFan
Outlaw 976 | ATI 2005 | M&K 850s Left, Center & Right, Surround-55s, MX-70B Sub | Harmony 950 remote | Panamax 5100 | OPPO UDP-203 | LG OLED55B7