The brush ismade from Bamboo and the bristles made from Sisal, what is Sesil ? It's a plant fibre. It is derived from an agave sort, agave sisalana, which is commonly referred to as sisal.
Being wonderfully durable it will last an age. When it finally gives up, you can simply replace the head with a shiny new replacement head. The old one can be composted, put in the wood burner or wood recycling at the tip.