I needed to replace the ones on my Yamaha cymbal stands so I grabbed the genuine Yamaha parts... They're a little pricey (you can buy a bag of 4 millenium ones for less than one of these) but they're quality. I bought the millenium ones for some cheap stands I have, they're fine but nothing on these.
I love the fact these screw onto the stand, it means they hold in place and don't fall off, slide up and down (or presumably vibrate loads when the cymbal is hit)
not much else to say, if you can afford the extra expense, you get the better quality, if you aren't fussy, there are cheaper alternatives.