We make the bottoms about 35 mm thick, and usually consist of 2 sheets of 15 to 18 mm on top of each other. an option is an aluminum plate between them so that the birds cannot easily gnaw through.
The inspection hatches are either a slider or a door, the PVC 400 and 500 mm diameter gray, cream, green or brown are standard with door. With the version of the door there is an aluminum border inside (see photo).
The PVC gray, cream, green, or brown colored are up to and including 315 mm standard with slider. the gray, green, or brown can also be fitted with a door
Furthermore, they are fitted with a mesh ladder and around the lid an aluminum rim is screwed in, 1.5 mm thick. in an aluminum U so that they are easy to replace.