These are dyed calf tails which are great for craft projects or fly-tying. These tails have the bone-in; the bone is thin. These tails are dyed right to the roots and an extra process leaves the tails very clean of dyes and natural oils. They are 10" to 12" (25 to 30 cm) long.
Cows are not an endangered species.
These skins are a by-product of the meat industry. The animals were not killed just for their tails.