The folding cups rotate on a 180-degree axis so DJs can beat-match using one side to listen to music while the other ear pays attention to the speaker, and the lateral adjustments also help the cups conform more tightly to your head. DJs will also appreciate the 6.5-foot wire that extends out of both cups in a Y shape and terminates in a straight plug that won't get in the way of a busy mixer. Shure also includes a quarter-inch threaded adapter.
The headphones weigh slightly more than half a pound with the cord included, but the plastic lining on the headband that keeps them light also makes them susceptible to creaking. The weakest part on headphones is the joint connecting the band to the earcups, so the SRH550DJ headphones' fragility makes me question their long-term durability, especially considering the rough way that travelling DJs treat their gear. However, the SRH550DJs get Shure's generous two-year warranty, which protects against structural damage.
The 50mm drivers behind each earcup deliver robust sound quality that holds its own against high listening volumes and sudden signal dips. Since these are entry-level headphones, you're not going to hear the balanced midrange shine you would with cans designed for natural audio mixing, but the overall tonal balance is appropriate for club DJs that listen at loud volumes.
DJs are also largely concerned with the soundstage of headphones, or how accurately they present the location of the instruments in relation to the microphones recording the music. The Shure SRH550DJs do a fine job of separating each instrument instead of mashing them all between your ears, and vocals are impressively precise as well.