The peak of the de-absorbed energy distribution of the TeV emitting blazars , all of the BL Lacertae ( BL ) class , can reach values up to \sim 10 TeV .
In the context of synchrotron-self Compton ( SSC ) models of relativistic uniformly moving blobs of plasma , such high energy peak emission can be reproduced only by assuming Doppler factors of \delta \sim 50 .
However , such high values strongly disagree with the unification of FR I radio galaxies and BLs .
Additionally , the recent detections of slow , possibly sub-luminal velocities in the sub-pc scale jets of the TeV BLs MKN 421 and MKN 501 suggest that the jets in these sources decelerate very early to mildly relativistic velocities ( \Gamma \sim a few ) .
In this work we examine the possibility that the relativistic flows in the TeV BLs are longitudinally decelerating .
In this case , modest Lorentz factors ( \Gamma \sim 15 ) , decelerating down to values compatible with the recent radio interferometric observations , can reproduce the \sim few TeV peak energy of these sources .
Furthermore , such decelerating flows are shown to reproduce the observed broadband BL - FR I luminosity ratios .