battery life. Compared to sound leveling, which brings all sounds, regardless of loudness, to the same level. Did not like they felt after I put them on Im trying to see if this sound will go away in a few days so I will update but so far its looking like I got a somewhat defective product. If youre willing to keep it plugged in most of the time to get the loudest sound and best clarity, arent expecting big bass, like the style, and get it for around $150, Id say its worth it for a medium sized room. Too harsh? Maybe, but it was disappointing to open a package with the wrong dress. Definitely run smaller than normal. Using the lift is simple. a narrower fit . But if there?s anyway to get the missing pieces let a girl know and I?ll change my review.