DSI Toy Battery Operated Slot Car Set. Turbo Challenge 300ZX Vs Supra. 1990. Condition is Used. Shipped USPS Ground. 1990 DSI ( diversified specialists inc.) #21649 turbo challenge road race set. Toyota twin turbo Supra vs Nissan 300ZX. The sides of the box were tapped to seal it. I bought this at a yard sale and it was Hot out and I didn’t realize that the tires on the rear wheels melted in the sun. Yet everything works and it’s complete! Very good condition for it’s age! Just needs some oil/ lube for the cars and a little sandpaper for the slots and a new home 😎 Refer to the pictures and thank you for looking.