Senshi armor is made of lacquered leather, hardened on the torso and in other places, presumably soft over or not covering the joints. It is said to have gaps in it, and the neck is a particularly weak point, being covered only by a thin screen of soft leather. It is not the hardest or the best armor, as it does not stop a katana or wakizashi, or even Horace's original sword. Senshi armor is marked with the wearer's clan emblem over the heart, and the armor of high-ranking Senshi is often lacquered a gaudy color, such as blue or even vermillion, like Arisaka's.
Noting that the armor is very weak, the Senshi probably relied more on their swordsmanship rather than their armour.