Opaque black mason jar sleeves block light to keep algae from growing in the water of Kratky method hydroponics systems. Printed in environmentally friendly PLA plastic.

Designed for quart sized mason jars, these sleeves block light from all sides except for a narrow viewing window. For better visibility inside the jar, I recommend slipping a piece of white paper inside the sleeve. A helpful cutout located halfway up the viewing window indicates the maximum fill level. Do not refill your Kratky jars above this tab or you risk drowning your plant's roots.

I can print jar sleeve other colors by request, but that may affect how opaque they are. Please message me for details.