What's all this about?

Mazda has shown two lightweight versions of the MX-5 Roadster at the SEMA show in Las Vegas.

Hold on, lightweight? Isn't the MX-5 pretty slim as it is?

Indeed so. The 1.5-litre model clocks in at just 975kg and the 160hp 2.0-litre, on which these two concepts are based, is claimed to tip the scales at 1,075kg.

So explain the one with a roof on it to me first.

The MX-5 Spyder is finished in Mercury Silver paint and its signature feature is a 'bikini top', designed to keep the elements off occupants, but to be even more simple than the folding manual roof of the road-going model. It also features a carbon fibre aero kit, an extra grille intake, a full-grain leather Spinneybeck Prima interior and some gorgeous, light (of course) 17-inch Yokohama Advan Racing RS II wheels clad in rubber from the same company.

And that mad blue one?

That's the Speedster, which does away with either a roof or a windscreen to absolutely maximise open-top motoring fun; you'd get plenty of flies in your teeth driving it, that's for sure. Even the doors and the seats are made of carbon fibre, while K&W coilover springs and dampers lower the car 30mm compared to the production Roadster. The final touch are those lovely 16-inch Rays 57 Extreme Gram Lights wheels and the colour, for reference, is known as Blue Ether.

Do they share any other components beyond the body panels on show and the chassis?

Not much, apart from Brembo four-pot calliper front brakes.

Will either get made?

It's highly unlikely, as the design manager for Mazda North America - Ken Saward - said they were purely built to 'show how the aftermarket can go wild on our flagship sports car while staying true to its mission'. If one was to go into production, our money would be on the Spyder ahead of the Speedster.