Nitro 1541H steel and 4340 alloy & chromium and molybdenum alloy axles commonly
known as "chromoly":
 
Our OE replacement axles are made of 1541H steel for a 25-35% increase in strength over their stock counterparts. Nitro 4340 chromoly axles are also heat treated but are designed with extra material for strength where it's needed. All of our axles are precision machined to OE specifications for excellent fitment.
 
1541H steel is a heat treated, carbon steel with .41% or less of other impurities. The heat treatments make the metal harder, with out making it brittle with a tensile strength of 181,000 psi. Up to 30% stronger than OE axles.
 
4340 cromoly steel, is a lower carbon steel with a minimum of 10% chromium by
weight. Known as a high strength, low carbon steel with a tensile strength of
228,000 psi opposed to OE 1040 steel with a tensile strength of 110,000 to
130,000 psi.
 
That means they take more punishment, to get you further down the trail or off
the trail entirely. That's Nitro Tough.