Tyre manufacturers Pirelli will bring an additional set of tyres to Bahrain for this week's second official pre-season test in order to test how the medium compound rubber performs without blanket warmers.
Tyre warmers will banned from 2015 and since Pirelli will provide the rubber to be used in the sport until the end of 2016 at least, the Italian company is eager to start reaching what compounds to use after this season.
"Pirelli are also bringing an extra set of medium tyres per team to Bahrain, with 2014 construction and compound," they confirmed to Sky Sports.
"However, these are actually considered to be 'prototypes' as their purpose is to test tyre behaviour without warming blankets, which will be banned from 2015 onwards."
Apart from that set of mediums, the various F1 teams will be handed 30 sets of tyres to be used in Bahrain this week.
The teams will be given a choice as to what compound tyres they want to use in eight of the sets, while the remaining 22 will be made up of a 'winter hard' compound - which warms up quickly during winter testing - as well as hard, medium and soft compounds.
"The first test of the year in Jerez was all about the teams getting their first taste of a very different set of technical regulations, so as expected running was limited and evaluating tyres was not a priority," Pirelli Motorsport Director Paul Hembery added.
"On top of that, winter conditions in Europe - even in southern Spain - are not representative of the race conditions we will generally encounter throughout the rest of the season. In Bahrain, we're expecting better weather and more running, which will allow ourselves and the teams to assimilate more data and knowledge of the tyres."