I designed this container to carry items like clean underwear/swimwear/gym-wear to/from the pool or gym, but you could really use it for anything.
The Screw-Top threads were a wee bit tight to begin with, but it loosens up as it's used.
You can print as many Extension Tubes as you like to screw together to add to your storage.
Extension tubes may need to print with Supports
EDIT: Fixed the bevel on the Extension tube so it shouldn't interfere with the thread.
Added an Extension Tube without the Divider so you can join an infinite number of them together for a super long transport tube for posters/etc.
EDIT 2: Fixed the Threads on the Extension Tubes. Due to not paying attention, I had incompatible threads on the Extension Tubes so they won't screw on properly if you printed the old versions. The Threads are now all M70x6
Printed with Hexagonal Infill (I was experimenting) which should give the container better rigidity but it won't matter too much.
Added additional Perimeters for added strength and thicker (1.5mm) Base & Top Layers.