That KJW is compatible with Tokyo Marui parts.
A metal slide/barrel set will probably run you more than half the cost if not more than the cost of the pistol itself. Plus, stay away from KJW if you are going for a Glock and go after the better brands like Tokyo Marui or KSCs or KWA's ATP (though its a full size pistol).
The internals of that KJW is spec'ed for use with duster gas. Hence the plastic slide. Where as Marui's will run on Green Gas out of the box. Hence, stronger internals.
If you are going to buy it, be prepared to open up your wallet.
"May you fight with the strength of ten full grown men."