Lightweight pulleys

[notgoodwithnames]

I'm pulling out my old stock radiator and replacing it and the clutch fan with brand new parts, along with some other front end stuff that's convenient to do while it's out, and I got to thinking... Is it worth buying the Greddy/Trust lightweight pulley kit? It's only 260 bucks https://www.rhdjapan.com/trust-greddy-pulley-kit-bnr32.html and claims to free up some response. But I can't seem to find definitive answers on;
Are they actually worth it
Are they a pain in the ass
Are they underdrive or standard belt size
I'm wondering if anyone can give me their reviews on lightweight pulleys and whether they'd be a nice QOL type upgrade if they're gonna be exposed and ready to swap out regardless or if they're just gonna be in there for looks. And if anyone can tell me whether or not these fit standard belt sizes, I'm seeing that Greddy discontinued their underdrive ones a while back but I'd like to confirm before I spend the money on them

[GTSBoy]

1 hour ago, notgoodwithnames said:

claims to free up some response

Yes. 1ms worth.

[E33]

Spend it on something better 

[Dose Pipe Sutututu]

$260 at a strip joint is money well spent, when compared to those pulleys

[Duncan]

I run them on the race car, but don't have anything back to back to show any difference. I have no reason to believe the "lightweight" does anything, but underdriving the alternator, water pump and power steering pump when using sustained high rpm in track use makes sense to me (you could also achieve this through a different balancer of course.)

Note the Greddy oversize pullies (water pump in particular) requires the standard harmonic balancer to be turned down a little in a lathe to clear the pulley.