Shimano MTB Bottom Bracket SM-BB52 With better sealing and rotation the SHIMANO DEORE bottom bracket delivers high driving efficiency. MODEL NO: SM-BB52 SERIES: DEORE M610 Series HOLLOWTECH II bottom bracket_Threaded bottom bracket type: Yes Threaded bottom bracket shell width (mm)_68: Yes Threaded bottom bracket shell width (mm)_73: Yes MODEL NO: BB-MT501 SERIES: DEORE M4100 Series HOLLOWTECH II bottom bracket_Threaded bottom bracket type: Yes Threaded bottom bracket shell width (mm)_68: Yes Threaded bottom bracket shell width (mm)_73: Yes The bottom bracket is a component of the bicycle, which connects the rear wheel and the pedal. The function of this part is to transmit power from the pedals to the wheels. It also supports rotation around an axis perpendicular to both its length and width. This article will introduce Shimano mtb bottom bracket SM-BB52/BBMT501 with box, which is one of Shimano’s MTB series products. Shimano mtb bottom bracket SM-BB52/BBMT501 with box has a diameter of 52mm and a thickness of 19mm, which are suitable for most mountain bikes. Its design can be adjusted by using two spacers that are included in the package or by using shimano mtb bottom bracket tool (sold separately). The body is made from aluminum alloy, while its bearing cage is made from steel alloy. It also has an external seal that prevents dirt and water from entering into it; this seal can be replaced if it becomes damaged or worn out over time due to exposure to weather conditions such as rain or mud. This product comes with four bolts (M6 x 1) that have nuts