Clear PETling without stopper.
A PETling is partly manufactured soft drink bottle. For this reason, the thread is the same found on virtually all soft drink bottles. The PETling is about 10 cm long and about 3 cm thick.
The container is watertight when an appropriate threaded stopper is used.
A PETling is a cache size micro.
The plastic type is Polyethylene terephthalate, or PET for short, thus the name. PETlings appear to be a German invention.