Review on Black Silicone Drink Coasters Set of 4 - Non-Slip 🍸 & Heat Resistant Cup Mats for Tabletop Protection & Furniture Safeguard by Billy Berry

Disappointed with the quality of these coasters. My expectations were modest - I needed a non slip coaster to secure my glassware to my glass table and they do an excellent job. However, the edges are rough and have strange stains that won't wash off (see photos). As they are for my use only I probably won't be returning them but I won't be buying from this company again.