MT-C is the shape and design as the standard "XP" high cut but uses the materials from the Ops-Core Maritime. The MT-C and Maritime helmets protect to the SOCOM standard
2 - Grain RCC - 4,075 fps
4 - Grain RCC - 3,450 fps
16 - Grain RCC - 2,425 fps
64 - Grain RCC - 1,700 fps
9MM FMJ RN (V0 at 0° Obliquity) - 1,195 fps threshold / @ 1,295 fps objective with 25.4 mm Backface Deformation
The Gentex TBH you linked uses aramid fibers while Ops-Core helmets use a blend of lighter HDPE and carbon fiber to achieve lower weight.
The Gentex TBH protects up to IIIA but at the expense of weight - it is marketed as a more cost effective alternative to the Ops-Core line of helmets or for departments that require full IIIA protection.