New observations for stars in the field of M 25 that exhibit bright U-band photometry. The intrinsic relation and reddening law by Turner (1989, and references therein) and Turner (1976) were adopted, respectively. A mismatch to the intrinsic relation appears just beyond A0 and may be indicative of a standardization offset or the Hyades anomaly. A mean cluster reddening was determined (E_B − V = 0.513    ±    0.034σ) from the B-stars to avoid the aforementioned problem (Turner 1979).