Practice pads are essential when learning, practicing and training, but ReelSkin is the best of the best. ReelSkin is designed to have a similar feel to human skin (it's actually a little creepy), allowing you to stretch the 'skin' while applying your tattoo. This practice material will hold a stencil transfer and also squishes like human skin.
These pads are as close to the real thing as you can get and they're even thick enough to be used on both sides, about 2-3mm!
Reelskin is handmade and can be wiped clean without leaving stains and smudges from ink or pigment.
You may also have searched for Reel Skin, or Real Skin.