Sienna Plein Art Glass Palette Insert: Medium, 9" x 10" Accessory for The Sienna Plein Air Pochade Box (CT-GP-0810) Accessory for the sienna plein air pochade box: glass palette insert only Made with tempered glass - much harder and stronger than regular glass The glass is very slick and durable. Smooth finished edges making them safe to handle and clean. Glass is a ideal surface to mix paint on.