I dunno, those are 60tpi which are different to the 300tpi 'open tubular' challenge tyres. My guess is vulcanised.
Also Challenge tyres are all made in Thailand.
Anyway, still these are the nicest tyres by far in that price range - show me any other clincher tyre with a herringbone or diamond pattern for under 20€.
You know that doesn't matter right?
@jetski started
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I dunno, those are 60tpi which are different to the 300tpi 'open tubular' challenge tyres.
My guess is vulcanised.
Also Challenge tyres are all made in Thailand.