Battery, YB9-B (Yuasa Brand)This is the replacement battery for a Genuine Stella (all model years) & Vespa PX150. It is an unsealed type, meaning that you can add distilled water to it to help "resurrect" it if gets low on juice. Yuasa is the best battery brand in the world and provides a long-lasting battery (assuming it's maintained properly). A sulfuric Acid pack is included. See our item battery tender for more information how to properly maintain a scooter battery.