Probing gamma-ray jets at different scales

Spectral Energy Distributions of large scale jets associated with three gamma-ray blazars have been obtained using Chandra and HST with the aim of comparing physical conditions in jets at different scales. New X-ray spectra for the blazar cores have also been derived. Modeling for each object the SEDs of the core (subpc scale) and large-scale (> 100 kpc) jet emission, we derive the properties of the jet at the two scales. The comparison of speeds and powers at different scales supports a simple scenario for the dynamics and propagation of high power relativistic jets.