This excludes slicks (you are allowed them in the open 400) but permits race intermediates such as Dunlop KR364. The 400s use road tyres mainly Pirelli super corsa and Metzler Racetecs, 250s favour the Michelin SM (Super moto) tyre - it is basically a 250 slick
Full wets are also allowed.
Not a lot in it between the best road tyre and so called race tyres.
Not sure what these new Dunlop 100 alphas are like as nobody has tried them.