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.
The new cheaper (lower TPI) versions of Challenge tyres come out of Duro in Taiwan
@Alb started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
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.