Lego® Technic 3743, 4205760 gear rack 1x4, toothed bar, black
LEGO Sets with Part 3743 Technic Gear Rack 1 x 4
Amazon.com: LEGO Technic NEW BLACK RACK GEAR SET Track Kit 1x4 brick Part Piece Mindstorms NXT robot robotics assortment pack ev3 motor (Pack of 10 pcs) : Toys & Games
LEGO part 3743 - White Technic, Gear Rack 1 x 4 at BrickScout