The soles on these shoes are natural crepe soles. Natural crepe soles are made of rubber or latex sheets layered together. The rubber is harvest from the rubber tree and gets processed and used to make crepe soles. Compared to other plastic soles, natural crepe soles are more environmentally friendly and sustainable as well.
Personally, I love crepe soles. Crepe soles are really comfortable and give a quite secure grip when you are walking. It is also very durable; it lasts very long. However, compared to leather soles or Dainite soles, it is less formal and more casual. So would not recommend it for black-tie events.
Unfortunately, crepe soles look very dirty when worn for a while. The soles get sticky when the weather is a bit hot, grab and collect all the dust from outside, and the colour turns black quickly. It is very durable, but the soles can crack if worn on a hard surface for a very long time.
The soles are Goodyear Storm welted. Storm welt a bit more advanced version of Good year welt that protects the shoes even better from the weather, hence the name storm welt.