Epoxy Capsule
One of the OP’s customers brought in a mysterious tube to the workplace. It contained a bit of fluid and several hard pebble-like objects inside. Unless the OP works as a mystery-object identifier, we have no idea why the customer even brought the thing to them. Good thing the person who posted this image knew where to find the answer: online.
According to some people, this is an epoxy capsule. You’re supposed to place the capsule into a hole in concrete, after which you drop a stud into the hole. The stud cracks the capsule, releasing the epoxy and creating a strong, weatherproof adhesive.