This 1/4 inch bulkhead has a 1/4inch BSPT thread so it screws into many of the gas fittings that we sell such as the MK4 Regulator body or gas manifolds.
With regards to tubing this is suitable to be used with this 1/4 inch PE tubing.
This fitting is typically used on mains water pressure and will adapt to many of the water filters sold commercially.