A Roller brake itself is enclosed in a drum and therefore is free from external influences such as rain and dirt

Splined mounts on the Roller brake locate directly on to Roller brake compatible Shimano Inter-M hubs

this appears to be the BR-iM80 Replacement or at least a renaming of the product. 

Large cooling fins keep temperatures down, eliminate fade and extend service life of the lubricant

Comes complete with M10 x 4.0 mm lock nut