The Crystal Glass Eggs are made of 100% hand-blown, premium Borosilicate glass. They are of the highest quality, and represent the most vibrant and durable glass products available today. The eggs can be heated or cooled to personal taste. These artistic gems are designed to bring pleasure to PC muscle exercises. Once inserted, they will help strengthen the Kegel muscle, while providing rippling effects of stimulation. At 1.75" x 1" (45 mm. x 27 mm.) in size, these eggs are a delicious, yet discreet item. Crystal premium glass eggs include a silk storage bag and a detailed instruction manual (that outlines PC muscle exercises designed to give pleasure and maintain healthy muscle control).