These legs are an alternative to the legs shown in the pictures, which are no longer available at Ikea. The closest Ikea solution costs 30€ : https://www.ikea.com/fr/fr/p/kallax-structure-blanc-40501892/
The central leg is not mandatory, it depends on the weight to support and the width of your furniture.
The files are compatible with wood screws M3, M4, and M5.
The length of the legs is 150 mm.
The tip is better printed in TPU.
The author hasn't provided the model origin yet.