Built-in button batteries, have 2 kind light: colorful light and white light, three model: Fast flashing, slow flashing, steady flashing. Acrylic material, water proof. Round shape dia: 3.94″, thickness 0.16″. The round LED luminous coasters can meet your needs in different occasions, such as parties, dating, family gatherings, annual company meetings, KTV, bars, cafes, disco clubs, slow clubs, leisure clubs, clubs, parks, gardens, restaurants, etc. Besides, also have square shape, octagon, thickness have 4mm and 10mm, price different.