What are they for Andy? Your bike or a track bike? I'd always recommend D209GP's for the NSR as they're pointier than the Pilot Race's and Corsa's and a proper race carcass. Don't confuse them with the GP racer Dunlop do...

I'm using 120/165 cut slick's on the 300 and they are effin' amazing. Used with warmers they feel way more stable than any tyre I've used and handling is perfect, but I'm also on the correct 3.5/5.25 rim sizes for this 250GP size combo... If it's a track bike, try them, they're KR106/KR108's and I'm using them in the medium soft/medium hard compounds. They wear very well.
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NSR300R - Why did i ever have a 250...