These sleeves fit quart size mason jars and act as a light barrier to keep algae from growing in the water. Printed from opaque black environmentally friendly PLA plastic.
I recommend slipping a piece of white paper inside the sleeve to help you see inside the jar better.
If they’re too small to fit around your jars (which is unlikely) just put them in the sun for 5 minutes to warm them up and gently uncurl them a bit. Don’t overdo it or you risk snapping the sleeve, though.
The tab that pokes into the viewing window is there as a visual guide for maximum fill level. Don’t refill your Kratky jars above that tab or your risk drowning your plant’s roots.
I can do other colors, but that may affect how opaque they are. Message me for details.