These are the guidelines:

• For use in a 16-ounce bottle, simply insert, tighten, and it's ready to use!
• For use in the 8-ounce bottle, trim off 1 ½ inches
• For use in the 6-ounce bottle, trim off 2 inches
• For use in the 4-ounce bottle, trim off 2 ¾ inches
  
  
• Regular household scissors should cut through the plastic easily. Use caution when trimming, as the snipped piece may fly in an unexpected direction
• To activate the pump's locking mechanism, simply twist the white top portion of the pump clockwise. To open the "lock", turn the top of the pump counter-clockwise in the direction shown on the top
• If your pump clogs, remove the pump from the bottle and flush it through with warm water. Shake or towel dry and replace in product.

Product Rating:   (3 reviews)

works well, but needs improvement
This pump is great quality, but the top of it is so smooth and curvy, forget using it when your hands are wet or have lotion on! A more 'shower-friendly' version would be much appreciated!
—Tamara

Worthless
Worst design. Spout is too small to get hand under and product dribbles down side of bottle. Too much effort to return. Rip off.
—Julie Boxley

Thanks for these!
These are great! They adapted well to my bottles and make using these great products so much easier, especially my facial cleanser. Perfect!
—Lavendar