I finally got around to making something I had kicking around in my head for quite some time. Unfortunately I just switched to powder nutrients, but these will go in my tool box because i'm sure I wont get everything I need all the time out of the powders. So I had this idea because I was noticing that my "part A" and "part B" liquid nutrients were not getting used up exactly the same. I was pouring the nutrients into a beaker that was not letting me be very exact with how much I was adding of each. My "part B" was getting used a lot faster then my "part A" just by me miss pouring a little each time I made a new batch of water for my plants. So this is what I did...... First I picked up a 10 pack of these at amazon. This is the second cap I fitted so I grabbed my cal/mag because I figure I will more then likely always have a need for cal/mag and measuring it. I decided to take pictures along the way to show you how I did this. So Take the cap off and drill a hold in the middle. I used a dremel tool to clean it up and get the hole a little larger then the drill bit so I could fit my syringe through the hole. I missed dead center, but who cares. I then used some goop I had laying around from another project. Put a little around the tip of the syringe. Inserted the syringe. Made sure it was gooped up real good and twisted it around to get the goop water tight. And BAM! Shits done. This cap will fit all my bottles of cal/mag with this size lid. I don't have to keep it on the bottle all the time, just when I need it. This one I made fits all my BCUZZ nutrient bottle and probably 95% of other manufacturers bottles. All I do is shake up the bottle and hold it upside-down, measure out exactly how much nutrients i'm using and untwist the cap. Never spill, and never guess how much I used. Anyways, I get excited over the small things. I can make these for people, but I don't have that many caps yet. If you want to send me a cap or a couple of them, let me know and Ill make you some. You just have to pay for the shipping and the syringe.