At some point between How to Train Your Dragon 2 and the third movie (a span of about a year), Tuffnut's armor was constructed.
This section requires expansion.
Tuffnut's dragon scale armor appears to be formed of several different pieces tailored to fit his body. There is the helmet, pauldrons, chest plating, a scaled cod piece, boxing-like gloves, scaled leggings, knee guards, and boots. There are also two wing structures kept folded for flight when needed. The suit is made out of Barf and Belch's shed scales, so has a predominantly green color. The scales appear to be attached to a leather base, presumably with Toothless' sticky saliva as the gluing agent. The whole suit is further embellished with a large number of large, metal-tipped spikes and a miniature head on the helmet resembling Belch.
Due to its construction from Barf and Belch's scales, Tuffnut's dragon scale armor is effectively impervious to fire. It is unknown if the non-scale portions are also treated in some way to be fire-retardant.
Like a suit of armor, it affords some protection from attack, much better than normal clothing. However, dragon skin and scales can be cut and pierced, so the armor is not fully protective from all attack.
- Though Tuffnut's dragon scale armor is considered fireproof, he wears his long hair outside of the suit, negating protection from fire.