Precision QCD in DIS at HERA

The HERA ep collider experiments have measured the proton structure functions over a wide kinematic range. New data from the H1 experiment now extend the range to higher 4-momentum transfer ($\sqrt{Q^2}$)over which a precision of $\simeq 2%$ is achieved in the neutral current channel. A factor of two reduction in the systematic uncertainties over previous measurement is attained. The charged current structure function measurementsare also significantly improved in precision. These data, when used in QCD analyses of the parton density functions (PDFs) reduce the PDF uncertainties particularly at high momentum fractions x which is relevant to predictions for the LHC experiments as well as low energy neutrino scattering cross sections