Precision W-pair physics with the YFSWW3 and KoralW Monte Carlos

We present the recent developments in the precision studies of W-pair and single-W processes in e+e- collisions achieved with the help of the KoralW and YFSWW3 Monte Carlo generators. We focus on the theoretical precision of the measurements of M_W and anomalous couplings on the example of lambda coupling. We present the mechanism of running these two independent codes in the form of one Concurrent Monte Carlo code. We describe also the extensions of KoralW necessary to emulate the kinematical region of single-W process.