Hi ..
I am thinking to buy the M1-L wRD16-II .. in the site has a option to change the rail to 210mm ... which rail that be changed ... the horizontal or vertical rail ? ... And what is the function of this 210mm rail ( I mean .. why I need to change to 210mm ) ?
BTW .. what is the weight of the M1-L wRD16-II ?

Thanks
Liao