I use EcoPoxy brand resin, which is plant-based, biodegradable, and non-toxic. These coasters start with a wide-mouth mason jar lid (gold). I then put a layer of real sand and lay a variety of different seashells and sea life over the sand, including starfish/sea stars, sand dollars, abalone shell pieces, scallops, and other shells. Resin is casted over the items to seal everything in, make it waterproof, and add a very slight blue mica sparkle to each coaster. All shells/items within the coasters are hand picked and arranged. The detail of the tiny sea life is breathtaking. Casting the shells/sea life in resin really makes it all pop and the slight mica powder shimmer adds to the beauty. Each coaster has a lip around the outside perimeter to help prevent moisture leakage. ***Your purchase will include twelve (12) coasters.*** Item Type: Handmade Dimensions (per coaster): 89 mm Weight (for 12): 4 lbs