It follows the large scaled turbine which led to the birth of the 90φ series. 
This volume and the minimum ground level are within the safety standard conformity. If combined with the Front Pipe PRO II it will be a step it up to the exhaust for race circuits. 

(SILENCE-VX PRO peculiar part ) 
It is aimed to increase torque in the mid-low speeds by improving the length to the "F" Pipe part and making it's chamber shape. Also, this achieves a higher response during high speeds by changing the main pipe's diameter to 90φ.
(Since Front Pipe PRO II is catalyst-less, it is for car racing only and not legal for street use. Moreover, if it is not combined with the Silence-VX PRO, it cannot be installed) 

*For race circuits only

Stock Model

Exhaust Diameter / Pipe Size

Material

NISSAN

SILENCE-VX PRO

Main Pipe : φ90 /  φ115

Stainless

For race circuits only

FRONT PIPE PRO II

φ70x2 -φ100 -φ90

Stainless

Even Length Type