This is a simple flat lid for my hydroponics set. When using less plants than the maximum, light was leaking into the water which created mold. These simple flat lids blocks the light from entering the hydroponics set. 

Link to set [https://www.aliexpress.us/item/3256806547258727.html](https://www.aliexpress.us/item/3256806547258727.html)

PS: the lid (cap) can be used for anything else.