This is an EDTA Throwing Dart from the movie Blade 1.

It has been modelled to fit a 16mm plastic Blood Collection tube (without a needle) and has a hole at the tip at 2mm in diameter to fit a needle that comes provided with most printer ink cartridge refill bottles.

It also comes with templates for mounting them to either a belt/leg harness using material, but they can be printed to be used that way as well.The sheath is also detachable from the back plate for easier printing.