Understanding TH350, TH400 Adjustable Modulator Options

All three of these parts from Rostra should be at the same base setting and perform the same out of the box. The addition of springs and a larger diaphragm area gives you two more options compared to the original (basic) modulator.

51-0062 – Original design.

• Color: Red
• Diaphragm Area: 1.7"

51-0017 – High performance spring for greater adjustment range.

• Color: Dual Red
• Diaphragm Area: 1.7"

51-0020 – Larger diaphragm for low-vacuum applications.

• Color: Black & Red
• Diaphragm Area: 2.4"