A ABSOLUTE MUST WHEN BUILDING YOUR SAKURA!
The original plastic pulleys work fine but if you lock a wheel bearing you will destroy the belt as well as the pulley that drives it.and unless you have the correct size pin punch needed to remove the spring pin from pulley you will have to cut the old one off.
Save yourself the inevitable hassle and up grade all of your pulleys ASAP.
A good improvement over the stock 13t pulleys for the D3. No more messing around trying to install spring pins, this pulley works with a grub screw. I would suggest grinding down a flat section on the Gear Box Shafts, perhaps with a Dremel like tool, to give the grub screw a good section to grip on to. Also, be careful when tightening the screw as I have found the gear thread strips a bit too easily. Other than that, a great part to get. You'll need three, two for the front and one for the rear.