Daler rowney acrylic stay wet palette packs large 290 x 520mmthese stay wet palettes work by osmosis keeping colours wet by moisture penetrating through the semi permeable membrane when not in use cover with the transparent lid which will reduce evaporation and keep colours workable for days add a little water to the reservoir and it will keep colours moist and workable for weeks comprises stay wet palette lid and refill pack for acrylic painting