time trial tyre
Deep section carbon fibre wheels have spurred something of a renaissance in tubular tyres; these Schwalbe Ultremo TT tyres only appeared in the German tyre company's catalogue a couple of years ago.
Like most tubulars, the Ultremo TTs are expensive compared to clinchers, and they're fiddly to fit and fix. On the flip side, carbon wheels for tubulars are cheaper, lighter and easier to make than carbon or carbon/aluminium clincher rims, which need a hook to hold the bead. So you could save money on your time trial wheels and tyres overall by choosing tubs.