Fits SentrySafe slim cabinets and many others; replaces the top wooden board. Holes are made for heat-sets, but some large self-tapping screws would also likely fit just fine.

This shelf allows for either a place to store desiccant and more top-shelf items, or cram it full of items on both shelves- it's up to you. :)

Holds one cheap hygrometer: https://a.co/d/i2cruHe