SGS3 Specs 1st stage:

• Weight:  Yoke 846g(1.87lb) Din 764g(1.68lb)
• High pressure port: (7/16″ 20W UNF) x 2
• Low pressure port: (3/8″ 24W UNF-2B) x 5
• Intermediate pressure: 130-145 PSI (9-10 Bar)
• Air supply 3364 PSI(232 Bar) for YOKE, 4351 PSI(300bar) for DIN
• Material: Marine grade SUS 316 body and components, Stainless steel springs
• The SGS3 uses an ultra-dense rubber membrane + heat conduction technology to prevent freezing
  in waters as low as 4°C.

SGt4 2nd stage specs:

Type: Balanced adjustable second-stage regulator
Easy-grip dive/pre-dive switch
Nitrox Compatibility
Inhalation effort: 1.2-1.5 CIW (Column inches of Water)
Heat Exchanger for Improved cold-water Performance (Metal Valve)
Spring re-adjustment system
Second stage adjustment knob: Fine-tunes inhalation effort.
Spring Re-adjustment
Weight: 297g(0.65lb)
Color available: Black / Silver / Colorful
Main materials: GF Enhanced PA, SUS 316 Metal Valve
Food-grade TPU mouthpiece
Reusable mouthpiece clamp
PVD coating