>>5713492>Which ones are better, the flat black ones or the grey wider ones?Pretty much depends on the scale you're building at. Neither one will roll on their own - Sets with the black treads tend to have a wheel inside of them that drives the treads. Sets with the grey treads get these rubber stoppers you put into the holes to give them the traction they need to actually roll. Check out the Fortrex, you can see the rubber pieces.
