This is a good tray to hold parts and hardware when working on repairing vehicles or just about anything where you are removing parts to reinstall later. The bottom is smooth and grips well on a curved surface like a car hood but also can sit in a warm engine compartment and will not melt unless it's directly on a very hot exhaust (over 400 degrees F). You can use this as a soldering tray, it won't melt and it holds PCBs in place fairly well.
I like the medium size because it's large enough to hold a lot of bolts and other hardware but small enough to fit just about anywhere. Also nice to have when working under a vehicle, the bright color is easy to see to place pieces as they are removed so they don't roll away or get lost. The material used is like a thick silicone, it flexes but it's somewhat firm and has a good amount of weight to it. The light green color does show dirt easily but cleans up ok with soap and warm water.
Tray has a handle and can be hung up or stored in or under a tool chest or on a shelf without taking up too much space. This is a very good quality tray that should last many years even with heavy use.