Extra Large Glow-In-The-Dark Cups. Serve big refreshments in these 42-oz. glow-in-the-dark plastic cups! Fun for serving party drinks, these giant green glasses will add a festive glow to any evening celebration. You can also fill them with candy and small toys for a party favor that’s sure to light up the night! From Halloween to 4th of July to prom or wherever, these extra large party cups make the perfect glow in the dark party supply for any nighttime party. 17.5cm Expose items to daylight to activate glow.