Three IKEA Eket shelves (70x35x70 cm) (https://www.ikea.com/de/de/p/eket-schrank-mit-4-faechern-dunkelgrau-00334536/)

and three shelves (35x35x35 cm) https://www.ikea.com/de/de/p/eket-schrank-dunkelgrau-50334591/#content). 50 Euro for all six shelves. Bought in 2019, still in good shape!