Building Blocks Kit - 1pcs High-tech Assemble 32531 4x6 Brick Building Blocks Kit - Aliexpress
LEGO Sets with Part 40344 Technic, Brick 4 x 6 Open Center
Technical Brick | Building Blocks | Toys - Gds-973 Brick 4 X 6 Compatible Lego 32531 - Aliexpress
LEGO PART 32531 Technic Brick 4 x 6 Open Center | Rebrickable - Build with LEGO
Amazon.com: Eske Kouri Gobricks GDS-973 Technical, Brick 4 x 6 Open Center Compatible with Lego 32531 All Major Brick Brands Toys Building Blocks Technical Parts Assembles DIY (194 Light Bluish Gray(071),10 PCS) :
Technic, Brick 4 x 6 Open Center : Part 32531 | BrickLink
LEGO (1x) Lt Gray Brick w/ Open Center (Choose Part 32531/40344 or 32532/40345) | eBay