KALLAX Shelf unit, black-brown, 44 1/8x44 1/8" - IKEA
Amazon.com: Ikea ' New KALLAX Shelf Unit, Black-Brown (White, 44 1/8x57 7/8) : Home & Kitchen
Amazon.com: ReplacementScrews Hardware Kit Compatible with IKEA KALLAX 3 x 3 Shelf Unit 404.156.01 - All Screws (104321) and Dowels (101339) : Home & Kitchen
Simple ikea kallax 4x4 model - TurboSquid 1523732
Kallax hack - the parts from a 2x2 and a 3x3 can be reconfigured to create two 2x3s. : r/ikeahacks