The durability of Pirelli's intermediate tyre impressed drivers during the first hours of today's Barcelona test.
The track was damp at the beginning of the day, allowing teams to run both the wet and intermediate tyre before it dried out.
While the dry compound tyres have degraded faster than most drivers expected, they found the intermediate stayed consisted as the surface dried.
"It was important to drive on intermediates today, to be honest I was quite surprised by them," Toro Rosso's Jaime Alguersuari told AUTOSPORT.
"The track was not completely wet, quite humid, and it was drying up. We were quite fast, able to run in the 1m40s and quite consistently. The tyre did not degrade at all."
Sauber Kamui Kobayashi agreed it compares well to Bridgestone's intermediate, but says the tyre's performance is not as good.
"It has a lot poorer grip but the consistency was better with Pirelli - that seems to be okay," he said.
"It's very difficult to judge where we have to be on the wet tyres or intermediate tyres. I think the compound itself is very hard."
Alguersuari tried to find a crossover point between the intermediate and slick tyres, but said he went a bit too early for the tyre.
"We tried the slicks in the wet and humid conditions and it wasn't really working," he said. "We needed to go back to the garage and wait a bit more time to go back and perform the same laptime on the slicks.