I am about to make some slate caves and rather than disturb my zebs for a measure I just want to make a size that most people have had success with.
Checking the various threads the dimensions that seem to work for everybody are Lenght 14cm Width 3.5cm and height 2.5cm these are all internall dimensions.
The average internal dimensions of my caves are 3.2 cm x 2.0 cm x 14.5 cm. I vary the sizes a bit some are lager and some smaller but we are only talking about mms either way.