All our coasters are designed by us, and inspired by real satellite height mapping data, adjusted to the British OS map projection. Our coasters are all engraved here in the Lake District and hand brushed in an ecofriendly protective sealant to help protect the coaster from marks. Each coaster measures approximately 10 x 10cm and comes with 4 small foam feet. Notes: Due to the nature of natural slate, each coaster may vary in size by 3mm, and the thickness can range anywhere from 3 – 6mm. Some coasters may feature a tiny shard or two of naturally forming pyrite (Also known as fools gold). In most cases (if precent at all) will be on the bottom of the coaster, but on occasion my be on the front. If this is the case, each coaster is checked by hand to ensure the impact on the design is at an absolute minimum. If your coaster does have a small shine, please be assured this is a perfectly natural element of authentic slate.