KALLAX Shelf unit with 4 inserts, white, 303/8x577/8" - IKEA
Ikea KALLAX Insert with 4 Shelves, White 13" x 13" 404.237.19 - NEW | eBay
KALLAX Shelf unit with 2 inserts, white, 161/2x577/8" - IKEA
Vertical Divider Insert for Cube Shelving – The Steady Hand
For those interested, Ikea has launched this Kallax variant with Vinyl enthusiasts/DJ in mind, it's called "Obegränsad" what do you think? price is 120€ : r/VGMvinyl
Display windows for IKEA® KALLAX unit — Wicked Brick
Amazon.com: IKEA Kallax Shelf Unit, High Gloss White : Home & Kitchen
KALLAX Shelving unit with underframe, black-brown/white, 577/8x231/4" - IKEA