I was lucky enough to find my set of Skullcandy MFM's on eBay for under $60 including shipping (new). XOXOXO! I have been using these bad boys ever since I got 'em. They came with a snap beanie for use in the cooler weather. They snap in place on the beanie minus the ear cups. The ear cups can be interchanged with ones from the G.I. series. They have 40mm drivers and deliver a great sound. The built-in mp3 player can be removed and loaded with music directly from a PC and used separately with most any other earphones. I have not been able to find the frequency response range. There has been written talk about a special screen from science of Qualcom, but if appears Skullcandy went with a liquid LED instead. The booklet included indicates the mp3 player is 512 mb, but it is actually 1 gb, enough for a lot of music. The power for the headphone's mp3 player comes from a battery chamber which hold 2 AAA batteries. Personally I use rechargeables. batteries. I believe these phones are from 2006-2008.