What is the difference between Romeo 4S and 4T?

The most noticeable difference between the Romeo4S and Romeo4T is the IPX rating and durability. the Romeo4T is rated specs call out:

Fully ruggedized and impact resistant for the toughest environments

Complete Mil-Spec 810G testing, submersible up to 20 meters

Waterproof, IPX-8 rated, and fog-proof.

Strong, lightweight 7075 Aluminum housing

The Romeo4S specs call out:

Extremely strong and light CNC aluminum housing

Strong, lightweight aircraft-grade CNC aluminum housing

Waterproof, IPX-7 rated, and fog-proof.