Aro-Flo Series Air Line Lubricator, 1/4 NPT Ports, 57 SCFM Flow Rating

This lubricator uses a 1/4" NPT port size.

Closer is better, and that's not just a general rule. These lubricators are designed to be installed as near to the downstream application as possible so the oil mist actually reaches the tool before it settles out or dissipates. The further away you mount it, the less effective the lubrication gets. If you've got multiple tools pulling off the same line, you'd want to think about positioning carefully so each one gets what it needs.