Yes, there are three holes in the top of the cap which are threaded for use with standard low pressure male nuts as shown below in the image.
This cap has 2 different size through holes which allows for two different size tubing or different venting while the other size (shown) has one size threaded hole for use with 1/8th” plugs or male nuts. For the through holes, two of them are one size and are for 1/8th tubing and the other one is for 1/16th” tubing.
Keeping these caps on the bottles with the tubing through it prevents dust and dirt from getting in and minimizes outgassing and absorption of CO2 from the atmosphere. However, these caps are not designed for applications which require sterility of the bottle’s contents. The caps do not fully seal on mobile phase bottles. They will not allow a vacuum to be created nor will they allow the bottles to be over pressurized which should always be avoided.
Click HERE for mobile phase delivery bottle cap ordering information and pictures