Drip irrigation, poly tubing and compression fittings come in many sizes, that unfortunately companies refer to as 1/2". It is measured o.d. (outside diameter, .580, .620, .700, .710....etc. If your poly is one size and you fittings another, they won't work, no matter what you do to it. Look on your poly, sometimes the size is printed on it, also on the fittings, sometimes there is a number stamped in the end to indicate the size. Where did you purchase your items. Good luck!

mp,

Did you match manufacturer's for your items? Technique of many manufacturers especially irrigation head nozzles to make other brands different from their own slightly to encourage(manipulate) you to replace needed items with their merchandise. This would not be unusual in my opinion. Smart from the seller's POV and irritating from the buyer's POV. Aloha