V2 Quick Connect, 19mm Male to 90deg 3/4in Barb
V2 Quick Connect fittings are found on many OEM vehicles including BMW, VW, Audi, Lamborghini, Ford, etc. These Radium Engineering fittings are used with many crankcase ventilation and turbo inlet connectors. They are primarily used for air/oil separation catch cans.
MEASUREMENT
No exact measurement from the actual fitting determines the size (in millimeters). The size is the inner diameter of the tube (or hose) that will be installed onto the fitting. Shown below is a 19mm V2 quick connect fitting. NOTE: it is not necessarily the ID or the OD of the fitting. The size will be in between these 2 values.

IMPORTANT: Always lubricate the mating O-rings with a light amount of oil prior to installing.
20-0748 V2 QUICK CONNECT, 19MM MALE TO 10AN MALE 90DEG
This adapts a 19mm V2 quick connect female to a swiveling 90 degree 10AN male fitting. As shown below, it secures directly to the following valve covers: Audi S6, S8, R8 as well as Lamborghini Huracan, Gallardo.

It is also compatible with the BMW Z4 and Toyota MK5 Supra (shown below).

Because it is 90 degree, it is perfect for 2nd generation BMW B58TU valve covers which have a vertical port, as shown above. Internal O-rings permit swiveling even after installation.
Engine Compatibility
-B58B30O1 (B58B30B)
-B58B30M1 (B58B30C)
-Audi/Lamborghini 5.2L V10
Machined from 6061 billet aluminum. For corrosion protection, they are anodized type-II. Stainless steel bolts are provided for securing the green retainer.