Difference between double front mech and triple

[wardie2000]

Could someone tell me the difference between a double front mech and a triple front mech. Is it the width?

Thanks

 

[sfcommuter]

Could someone tell me the difference between a double front mech and a triple front mech. Is it the width?

Thanks

straight from sheldonbrown.com:

Double/Triple
Modern derailers are optimized for either double or triple chainwheels. The shape of the shifting cage is tailored for the application intended.

"Double" front derailers have inner cage plates that extend down slightly farther than the outer plates.

"Triple" front derailers have extended inner plates that go down considerably lower than the outer plates.

"Double" front derailers will work with triples, but if the middle ring is much smaller than the big ring, they will be balky shifting up from the small to the middle chainring.

"Triple" front derailers may have interference problems between the extended inner plate and the inner chainring.