Slower speed for hi-altitude or hot conditions. At sea-level, flies most like feather birds. Nylon Shuttlecocks: A MAVIS shuttle recovers in a fleeting 0.020 sec! Products of precision manufacturing, Yonex Nylon Shuttlecocks closely approximate the fast recovery, peak & drop, and flight trajectory of feather shuttlecocks. In smash-speed tests to 300kmph, Mavis-350 consistently recovered in 0.020 sec., only 0.005 sec. off the 0.015 sec. recovery time of Yonex Feather Shuttlecocks. The performance mix of fast recovery, consistent peak & drop, and highly accurate trajectory fills rallies with enjoyment. Quantity discount for schools and clubs, please call for price!!!