"McClain learned during her first spacewalk that a medium-size hard upper torso — essentially the shirt of the spacesuit — fits her best. Because only one medium-size torso can be made ready by Friday, March 29, Koch will wear it", NASA said in an official statement.
According to the agency, astronaut Nick Hague will participate in the spacewalk outside the International Space Station with Koch.
Earlier this month, the crew pointed out that suit sizes might be an issue, as McClain stated on her Twitter page that she had become 2 inches (5 centimetres) taller due to space growth.