Shimano Tiagra RD-4601-SS Rear Derailleur 10sp

Wider range 10sp
As low as 11 tooth min., up to 30t max
Enhanced cable pulling
Less effected by outside factors
Wide link alloy body
Short Cage (SS): 30t max cog; 16t max chainring difference; 33t wrap capacity
Medium Cage (GS): 30t max cog; 22t max chainring difference; 39t wrap capacity