3 ms·6.35 mm jacks are quite a lot more robust than their smaller 3.5 mm brethren.by formerly_proven 6y ago6.35 mm jacks are quite a lot more robust than their smaller 3.5 mm brethren.trasz 6y agoWhich can be a problem when you plug them into the phone - you probably don't want your plug to be more robust than the socket.leetcrew 6y agoyou might if your headphones are worth more than your phone ;) I doubt many people are trying to drive HD-650's with a phone anyway.