The Builder Parts Collection is Bandai's official line of accessory and customization sets for Gunpla. Instead of full mobile suit kits, these are the pieces you wish came in the box with your model: extra hand parts, thrusters, verniers, weapons, emblems, effect parts, display bases, and detail accents. They slot straight into existing builds, so you can dress up a basic High Grade or give a stock kit some serious attitude without hunting for third-party alternatives.

The line comes in 1/144 and 1/100 scales with a few non-scale releases, so coverage spans High Grade, Real Grade, and Master Grade kits. It splits into three branches: System Weapon for modular weapon sets that ship with display racks and extra hand parts, System Base for adjustable stands and hangar-style dioramas, and Builders Parts HD for high-detail accent pieces like v-fins, piping, MS hands, and effect parts. Everything is snap-fit and uses the same polystyrene as regular Gunpla, so cutting, sanding, priming, and painting work exactly the way you already know. Most BPHD sets come in neutral gray, making them easy to drop into any color scheme.

These are the sets that turn "good enough" into something personal. Swap out soft factory hands for sharper Builders Parts HD replacements, load a custom suit up with System Weapon bazookas and beam rifles, stage your finished build on a System Base, or drop in effect parts to fake muzzle flash and beam trails in photos. Most pieces use 3mm peg connections or standard HG/RG hand joints, so compatibility is rarely an issue. If you're into Gunpla customization, kitbashing, or just want more presence out of your builds, this line is where to start.