Overpressure relief valve (OPRV) for lift bags and other buoys; prevents overpressure and rupture while remaining lightweight, strong and portable. You can quickly vent air as needed to avoid accidental overinflation during inflation, enabling safer, longer use in diving and lifting operations. Easy to assemble and use; attached with a drawstring for simple installation on lift bags and buoyant devices. ABS body, rubber washer and corrosion-resistant steel spring provide durable performance in challenging diving environments. Compatibility and performance: designed for lift bags and other buoys using overpressure protection; suitable for standard dive setups and field use. Use scenarios - Lifting bags during underwater operations (wreck salvage, underwater construction) to regulate air volume and prevent bag rupture. - Managing buoyancy for surface buoys and signaling buoys during deployment, transport, or storage to prevent overinflation. - Training or field testing of buoyancy systems, allowing quick venting to fine-tune buoyancy control.