I think HKS went threw 3 designs, the first gen one has the adjustment screw, the next one looks exactly the same but no adjustment screw and the third one now has the fins/heatsinks
The old one cost more from what Ive seen, because their "rare" its adjustable so you can make it release harder on lower rpms I guess... The New new one just looks goofy though, I really dont think theres a need for the "heat sink" not to mention the b#tch it would be to clean.... The second gen is a basic bov, I like mine. You can also buy different fittings for all of them to have slightly different sounds.