The strength of an Arrancar's Hierro is dependant on their Spiritual Energy, this was noted by Nnoitra Jiruga by which exclaiming that he has the strongest Hierro out of the Espada. However it was never revealed if this were true or not as he it outranked by 4 other Espada, and an Ex-Espada was able to injure him without any reciprocation. Although Hirro allows an Arrancar to block bladed attacks from Shinigami, Kenpachi Zaraki was able to cut Nnoitra by adapting to the latters Riatsu.
This technique is exclusive to Arrancar, as Menos level Hollow have not shown the ability to use this technique. It is also unknown as to whether Visoreds can use this technique. Shinigami have a similar technique in which they can use their Riatsu to block oncoming attacks, this was shown through Ichigo's battle with Ex-Captain Shūsuke Amagai. Also during Ichigo's battle with Kenpachi, he was unable to cut him even after given the opportunity to do so. However this technique does not reach the strength of Hierro.
When Ichigo is in is half transformed Hollow state, he exhibited a similar technique in which he was able to endure several injuries inflicted on him by the Visoreds during his training. He was shown doing this by regenerating with bone like carapaces that appeared to be just as resistant as Hierro, if not so more.