As we move toward later types along the main sequence after G0, we note that the hydrogen lines continue to fade, while the strength of the general metallic-line spectrum continues to increase. The G-band continues to increase in strength until the early K-type stars (about K2), and then begins to fade. The Ca I 4227 line grows gradually in strength until the early K stars, and then becomes dramatically stronger by mid-K. The ratios Fe I 4046/H and Fe I 4325/H are useful in estimating the temperature type, reversing at a spectral type near G8. Unfortunately, these ratios are not reliable in metal-weak or metal-strong stars. The temperature type may be estimated with precision, even in metal-weak stars by using the ratio of the Cr I 4254 line with the two neighboring Fe I lines at 4250 and 4260. The position of these lines is indicated on the illustration by the three tick marks immediately below the G0 V spectrum. Notice that the Cr I line (which arises from a low-lying level) becomes stronger in ratio with the two flanking Fe I lines, being clearly stronger than both by K5.