The combination of close-to-feather shuttlecock flight performance and four to five times more durability than an ordinary nylon shuttlecock makes the YONEX MAVIS series the most cost-effective choice for practice sessions. The hardness of the skirt – the feather part of the nylon shuttlecock – varies depending on temperature. Natural Cork GREEN CAP: SLOW / 22ºC~33ºC BLUE CAP: MEDIUM / 12ºC~23ºC RED CAP: FAST / 0ºC~13ºC