This is the 28mm water cap. It’s cheap and useful. It has two kinds of caps we produce now: 28mm PCO 1810 and 28mm 1881. The 28mm PCO 1810 cap height is a little higher, and the 28mm 1881 height is a little shorter. Before you will order the cap from us, you can send your own preform samples to us, for checking if the cap and preform is really in good match. If it has any error, we can depend on your samples to modify the our mold. Normally, the MOQ for 28mm water cap is 100,000 pcs, and you can also order any color you want.