What's the difference between Zinsser 123 and Zinsser 123 Plus?

What's the difference between Zinsser 123 and Zinsser 123 Plus? Zinsser Bulls Eye 1-2-3 and Zinsser Bulls Eye 1-2-3 Plus are both water-based all-purpose primers, but Plus is enhanced version. Original 1-2-3 is versatile primer and sealer for interior and exterior, good adhesion on many surfaces, blocks light to medium stains, low odor, and can be used on drywall, wood, masonry, metal, and glossy surfaces. 1-2-3 Plus adds extra features, it is high-performance with added mold and mildew resistance, better stain blocking than original, and includes biocides to protect dried film from mold growth, making it better for humid areas like bathrooms, kitchens, and basements. Plus also has improved adhesion and hide, and is often marketed as primer with odor blocking and mold protection. Both are water-based, low VOC, easy cleanup, and topcoat in 1 hour. So difference is Plus has added mold resistance and improved stain blocking, suitable for damp or stain-prone areas, while original 1-2-3 is standard all-purpose for general priming. Price for Plus is slightly higher due to enhanced formulation.