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.
14-0363 V2 QUICK CONNECT, 19MM FEMALE 10AN MALE STRAIGHT
This fitting adapts the male side of a 19mm V2 quick connect to 10AN male.
Engine Compatibility
-Audi A4 (2.0L TSI)
-Audi A5 (2.0L TSI)
-Audi A6 (2.0L TSI)
-Audi TT (2.0L TSI)
-BMW 135i/335i/535i/740i (N54)
-BMW 325i/330i/525i/530i/X3/Z3/Z4 (M54)
-Ford Fiesta ST/Focus/Escape/Fusion (1.6L EcoBoost)
-VW Beetle (2.0L TSI)
-VW Golf GTI MK6 (2.0L TSI)
-VW Jetta (2.0L TSI)
-VW Tiguan (2.0L TSI)
*These adapters are compatible with many engines not listed. 
Machined from 6061 billet aluminum. For corrosion protection, they are anodized type-II. 
14-0668 V2 QUICK CONNECT, 19MM MALE TO 90DEG 3/4IN BARB
This is a 19mm V2 quick connect male hose end that connects to a 19mm female V2 quick connect.
Engine Compatibility
-VW Golf R MK7 (EA888)
-VW Jetta (1.8L EA888 TSI)
-VW Passat (1.8L EA888 TSI)
*These adapters are compatible with many engines not listed. 
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.
20-0758 V2 QUICK CONNECT, 19MM MALE TO 10AN MALE STRAIGHT
This adapts a 19mm V2 quick connect female to a 10AN male fitting. It secures directly to many BMW valve covers.
Engine Compatibility
-Audi A4 (2.0L TSI)
-Audi A5 (2.0L TSI)
-Audi A6 (2.0L TSI)
-Audi TT (2.0L TSI)
-BMW 135i/335i/535i/740i (N54)
-BMW 325i/330i/525i/530i/X3/Z3/Z4 (M54)
-Ford Fiesta ST/Focus/Escape/Fusion (1.6L EcoBoost)
-VW Beetle (2.0L TSI)
-VW Golf GTI MK6 (2.0L TSI)
-VW Jetta (2.0L TSI)
-VW Tiguan (2.0L TSI)
*These adapters are compatible with many engines not listed.
Because it is straight, it is perfect for 1st generation BMW B58B30M0 (B58B30A) valve covers that have a horizontal port, as shown below. 
Also, compatible with many BMW engines (S52 shown below).
Machined from 6061 billet aluminum. For corrosion protection, they are anodized type-II. Stainless steel bolts are provided for securing the green retainer.
20-0531 V2 QUICK CONNECT, 19MM FEMALE AND 19MM MALE TO 10AN MALE
This kit adapts both sides of a 19mm V2 quick connection (male/female) to 10AN male.
Engine Compatibility
-Audi A4 (2.0L TSI)
-Audi A5 (2.0L TSI)
-Audi A6 (2.0L TSI)
-Audi TT (2.0L TSI)
-BMW 135i/335i/535i/740i (N54)
-BMW 325i/330i/525i/530i/X3/Z3/Z4 (M54)
-Ford Fiesta ST/Focus/Escape/Fusion (1.6L EcoBoost)
-VW Beetle (2.0L TSI)
-VW Golf GTI MK6 (2.0L TSI)
-VW Jetta (2.0L TSI)
-VW Tiguan (2.0L TSI)
*These adapters are compatible with many engines not listed.
Machined from 6061 billet aluminum. For corrosion protection, they are anodized type-II. 
Stainless steel bolts are provided for securing the green retainer. An oil resistant Buna-N O-ring is used for sealing.
