How does the “undefined” product on this page (http://tools.woot.com/offers/safety-works-am-fm-mp3-ear-muffs-8?ref=cnt_wp_0_1) work with MP3? Does it have a built in player or SD slot?
Sorry about that, we changed the name back 
I was also told “The MP3 function works via the Aux jack cord.”
Wow, Amazon really doesn’t like these. http://www.amazon.com/MSA-Safety-Works-641817018705-Protector/dp/B002FYGUL2
One presumes these are battery powered but neither the “decripton” nor the “specs” makes mention of batteries, either size or number.