Regular edition Hot Wheels are 1/64 scale (S scale). However, Hot Wheels has on a couple occasions, experimented with 1/87 scale. Most recently was I guess early last year. Some of the cars that were popular in 1/64 scale, were also released in 1/87 scale. But while the 1/64 scale Hot Wheels were a dollar or less, the 1/87 scale versions were $3 or $4 each. They didn't sell well and many that were planned (like a 67 Pontiac GTO and a 62 Chevy Bel Air), were cancelled before they made it to production. Among the ones that made it to production and looked the least toy-like, were the 70 Dodge Challenger in Plum Crazy Purple, the 70 Plymouth Superbird in Top Banana yellow, the custom 64 Ford Galaxie 2 door hardtop, and the 55 Chevy 1/2 ton panel truck. But, the wheels on all of them are way too big. A wheel swap goes along way on these towards making them usable on an HO layout.