From Trojan's web site:
Trojan’s Plus Series™ deep-cycle batteries deliver unrivaled premium features and benefits to our customers and include our exclusive Maxguard® Advanced Design Separator and Alpha Plus® Paste with T2 Technology™.
These features and benefits include:
Trojan’s SureVent™ flip-top vent cap system, making watering your battery safer, faster and easier.
Trojan’s vent well offers a built-in maximum level indicator for precise watering resulting in better performance and longer life.
Trojan’s embedded terminals provide higher durability.