I have found the better fitting for nylo flow tubing

 

 www.andersonmetals.com      part # 02668-0402        this one is 1/8 pipe and ¼ tube  these have a built-in insert    that works better than any I have found to date

 might have to order them through    www.mcmaster.com

 

 parker seems to leak and loosen a bit      

 

 

 Bill Maddox