Cycling UK Forum

I've just taken the BB (Shimano UN55) out of my bike for the first time and it has MM 110 on it.

I'm wondering what the 'MM' means as other BBs I've had have 'LL' on them (and as per the library pic below)

Thanks.

Shimano BB's are marked with letter codes that correspond to different spindle lengths e.g.:-

Code Length
MM 107mm and 110.5mm
LL 113mm
D-H 115mm
YL 116mm
XL 118mm
ZL 121mm
NL 122.5mm
EL 127.5mm

Edit: I forgot to say some codes indicate spindle offset as well.