Our Hellbender 70 bottom brackets feature our Hellbender bearings - a stainless steel bearing with grease. With bottom brackets, the biggest killer is corrosion, and stainless steel bearings have significantly more corrosion resistance than non stainless steel bearings. Despite the seal, contaminants can still enter the system and the Hellbender bearings can be cleaned and re-greased when needed. The stainless steel bearings were also designed to be very long lasting, and they have slightly less drag than our MTRX bearing, making the Hellbender 70 ideal for the rider that may prioritize efficiency over durability