This pic shows some of the possible fittings that I might use when doing an oil tap.

The two Tees shown are both 1/8 NPT Tees; the difference in appearance is due to the different manufacturers.

The lower Tee, which has the nylon tubing attached, also has a 1in long "close nipple" threaded in the side of the Tee. The oil tap in the block in the previous pic also has the 1in close nipple; but it was covered up by the protecto-wrap.

When possible, I prefer to use the 1in close nipple: the hex center makes it easier to tighten the pipe into the block threads; or into the cylinder head...when I do an oil tap at the rear of the head.

The various lengths of pipe that I use are shown: from a 3/4in close nipple to a 2in length piece of pipe