This is one of Escher's tesselating fishes in 3D. Several of these fishes can be grouped together, so that they form a never ending pattern.
See also: http://www.quirxi.net/misc/lizard_tutorial/index.html.

This is one of Escher's tesselating lizards in 3D. These lizards can be grouped together, so that they form a never ending pattern.
See also: http://www.quirxi.net/misc/lizard_tutorial/index.html

This is a mold pattern for a single 12mm roundball bullet. This kind of typically cast in lead and used for slingshot shooting. The model is hollow inside and has two drains, which makes printing a bit cheaper. But you will have to close the openings before using it.

This is a mold pattern for a single 8 mm roundball bullet. This kind of typically cast in lead and used for slingshot shooting.

This is a mold pattern for a single 10mm roundball bullet. This kind of typically cast in lead and used for slingshot shooting.

Simple western style hunting slingshot.