Venier pulley - catcams Vs piper

[cartledge_uk]

As the title, I'm after one. But which should I get?

Does anyone have any figures on weight difference between the 2?

Does one have more adjustability? Etc

 

[DOH]

Do you mean an adjustable Vernier Pulley?
If so why would this be needed on a 1.7 because all the pulleys are floating ie no keyways?