They’re typically made from polyester or soft faux fur.
Most tails attach with a hook-and-loop fastener (Velcro) and often include a loop or strap that secures to a belt loop or other part of your outfit.
Most listings are one-size or 'uni-sized' designed to fit most adults; some explicitly note fit for children ages 3 and up, and a few items show Mens/Womens sizing fields.
Kits are typically two pieces: an ear headband (or separate ears) plus a tail.
It varies by listing: some sets are labeled for adults, while others are unisized to fit both adults and children aged 3 and up.
They’re quick to put on—listings note you can transform in under a minute and that the set requires little or no setup.
They’re sold as costume headwear for animal-themed dress-up and quick Halloween costumes.