what's the difference beside the obvious number - is there really an advantage between the 2 ?

With 130, the smallest you can go is 38 teeth. If you want compact gearing, you need 110. In theory, the larger spider diameter on 130 makes for stiffer rings, but I don't think there's a measureable difference in reality.

so this is a wrong ad then ?
Important Information:

Model:

Shimano Ultegra Compact 10 Speed FC-R600

Size:

172.5mm

Chainrings:

Shimano Ultegra BCD Is 130mm

34 x 50

what's the difference beside the obvious number - is there really an advantage between the 2 ?
The 110mm BCD (now called a compact crankset) allows the use of smaller chain rings such as the popular 34/50 or 36/50. The smallest you can put on a 130BCD is 38 teeth. - TF

so this is a wrong ad then ?
Important Information:

Model:

Shimano Ultegra Compact 10 Speed FC-R600

Size:

172.5mm

Chainrings:

Shimano Ultegra BCD Is 130mm

34 x 50
Yes it is wrong. The FC-R600 is not an Ultegra. An Ultegra is 130. The 34/50 R600 is 110mm. - TF

so this is a wrong ad then ?
Important Information:

Model:

Shimano Ultegra Compact 10 Speed FC-R600

Size:

172.5mm

Chainrings:

Shimano Ultegra BCD Is 130mm

34 x 50

If it's really acompact with 34/50, it's 110.

... and the R600 is considered the 105 level compact. The R700 was the Ultegra level compact.

cool thank you - that was an auction from ebay ..jus wanna make sure I get the right one . THanks guys