Review on Leak-Proof Screw Cap Glass Test Tubes Set of 6, 85mm Length with 5 ml Marking, Perfect for Aquarium Water Tests - Tililly Concepts by William Hilzer

I use them fairly infrequently (once a month, not all tubes are used every time) for API aquarium water testing and I've only had them for 8 months. There is no more lettering on the outside, so adding 5ml is difficult. Also, sometimes caps screw straight on and sometimes they don't, no matter how carefully I screw them on, and unless screwed straight on, they leak badly. They're narrower than API tubes, meaning they're easy to miss when adding drops. Their narrow openings also mean that surface tension can prevent liquid from spurting out of them when they're inverted - sometimes you need to flip and shake instead of just flipping.