Correct neck finish will ensure trigger sprayer perfectly fit on paired bottles, the basic principle is use the same standard. For example, 28/400 bottle neck should pair with 28/400 trigger sprayer.
However, there is a funny phenomenon. Take 28/400 for example, We know 28 refers to the outer diameter of bottle neck which is 28mm, and 400 refers to the thread type. Many U.S. packaging manufacturers declare that 28/400 should have one full circle thread corresponding to bottle/closure finish standard issued by Glass Packaging Institute (GPI), but for some unknown reason, many China manufacturers regard one and half circle thread as 28/400, which should be 28/410 according to standard.
I don’t know what the reason is and this certainly cause many unpleasant misunderstanding and problems, we have to send new samples to customers sometimes. So we encourage if possible, send technical drawing of target bottle to your trigger sprayers supplier to avoid this happen. And leaking test is essential for sample test.