1/2" fittings come in 3 'sizes' because of the 3 different sizes of 1/2" poly tube so here we go!

The three (3) common sizes of poly tube (Smallest to Largest)

1. .520 I.D. x .620 O.D.
   
2. .600 I.D. x .700 O.D.
   
3. .610 I.D. x .710 O.D.
   

I.D. = Inside Diameter - O.D. = Outside Diameter

Style of fitting

• Universal Nut Lock - Works with All 1/2" tubing sizes
  
• Spin-Loc - Works with All 1/2" tubing sizes
  
• 16mm Barbed - Works with .520 x .620 or 16mm Dripperline
  
• 17mm Barbed - Works with .600 x .700 or 17mm Dripperline
  
• Compression Style:
  
• With GREEN ends - Works with .520 x .620 or 16mm Dripperline
  
• With BLACK ends - Works with .600 x .700 or 17mm Dripperline
  
• With BLUE ends - Works with .610 x .710 Tube