K-corrections in the r band for our SN sample. For each SN redshift we determined the from all the SN spectra in our sample, and we fit them with a second-order polynomial, shown as a solid red line. The 1σ uncertainties are shown as red dashed lines. The SNe are ordered based on redshift, with the nearest ones on top. For the most distant events, K-corrections in r have values up to 0.4 mag around peak. For comparison, in blue we show the K-corrections from the SN Ic-BL spectral templates available at Peter Nugent’s Spectral Templates webpage. The results are similar and compatible within the uncertainties.