The Siemens 3VM9152-0QC00 is a broadened front-mounted bus connector, sold as a 2-unit accessory for 3VM11 2-pole molded case circuit breakers. It's designed specifically for those breakers and carries a voltage restriction: only usable up to 240 V AC, because it lacks additional insulation for the mounting plate or rear panel. If you're wiring a panel that runs 3VM11 breakers above that voltage, you'll need a different bus connector — this one won't meet the clearance or creepage.
Mounts broadened front — meaning it sticks out a bit wider than a standard bus connector, which can help with wire routing or finger clearance in a crowded enclosure. Packaging dimensions are 120 x 170 x 15 mm, so it'll fit through a standard panel knock-out or DIN-rail gland plate without trouble. The product class is B: return restricted, so if you're stocking spares, make sure the order is right the first time — Siemens requires direct contact for returns.