McLaren has revealed the Honda-powered MP4-31 Formula 1 car it will race in the 2016 season.
The team laboured through a disastrous 2015 campaign as Honda struggled on its return to F1, finishing ninth in the constructors' championship.
Jenson Button will be behind the wheel for the new car's first laps on Monday, during the opening day of pre-season testing at Barcelona.
"As we embark on the second year of our renewed McLaren-Honda partnership, all of us remain united in our purpose," McLaren group CEO Ron Dennis said.
"That purpose is to develop our team towards our shared ambition: to win.
"We'll make no predictions as to when those wins will come, but I can say without fear of contradiction that every member of our team has worked with truly relentless dedication over the past few months.
"The result is that MP4-31's developmental trajectory has been usefully steepened over the winter, and I'm consequently very proud of our team's efforts."
McLaren describes the new chassis as 'innovative', and its fortunes will rest on Honda's off-season progress with the RA616H power unit.
"Learning from last year, we've made changes to the compressor and other hardware of the power unit during the break, maturing our overall concept from last year," Honda motorsport boss Yasuhisa Arai said.
"Our focus will be to test the car's balance with the new chassis and power unit, and specifically the ERS direction during the eight days of winter testing.
"We won't know exactly where we stand until we reach the end of the two tests, but we're looking forward to getting back on track, gathering data, and feeding back the information to our engineers so as to prepare for Melbourne and onwards."
AERO IMPRESSES DRIVERS
McLaren retains its 'size zero' aero philosophy with the MP4-31, and Button and team-mate Fernando Alonso noted the detail of the package.
"The immense amount of sheer hard work that has gone into the development of the MP4-31 over the winter makes me immensely proud, and consequently I go into the new season with even more motivation and belief," Button said.
"From what I've seen so far, the aero detailing on the car looks fantastic, and I'm really looking forward to beginning the process of testing those new innovations when I get behind the wheel tomorrow."
Alonso will test the car on the second and fourth days of this week's test.
"The aero package shows fantastic attention to detail," the Spaniard added.
"The whole car is beautiful in fact - it's particularly nicely packaged from an aerodynamic point of view."
Autosport will provide comprehensive live commentary and analysis from all eight days of pre-season F1 testing plus the team launches