In a small workshop just outside Tokyo, mechanics hammer, weld and measure as they craft "the Porsche of wheelchairs" for the world's top Paralympic athletes ahead of the 2020 Games. Paralympians using wheelchairs built by OX Engineering, a small company in the city of Chiba, have won a total of 122 medals since 1996 - making them the gold medal champion among Japan's main manufacturers.
Since Tokyo won the bid to host the 2020 Olympics and Paralympics, orders have flown in, increasing by around a fifth every year. The firm now makes about 500 sports wheelchairs a year for athletes from 21 countries.
"We have the technology to make a wheelchair fit perfectly for each athlete and to help them perform at their best," company president Katsuyuki Ishii told AFP.
OX Engineering was founded in 1988 by Ishii's father Shigeyuki who used to sell motorbikes until his life was turned upside down by injury.
Road-testing a new bike, he had an accident that caused spinal injuries and left him paralysed.
Manufacturing sports wheelchairs is high-precision work - they have to be specially designed for speed and agility, depending on the sport.
Tennis wheelchairs, for instance, have two large, angled wheels for stability in quick turns, with two casters wheels at the front and one at the back.
Racing wheelchairs, on the other hand, look completely different, with two large rear wheels and one small front wheel connected by a long shaft.
The detailed process of designing and manufacturing wheelchairs at OX Engineering remains top secret, but one of the ways the company pioneered to enhance athletes' performance was to boost the durability of the vehicle.