The paper deals with He-Ne lasers at 633 nm, frequency-stabilized by saturated absorption in ¹²⁷I₂. The procedure of iodine cell cleaning and filling is presented in detail. This technology provides long-term reproducibility of laser frequency as may be seen from measurements taken over a four-year period. The paper shows the hyperfine spectrum of a fused silica laser with eighteen hyperfine components obtained by a third-harmonic detection technique and mean frequency differences resulting from comparisons with the standards of the PTB (Braunschweig) and the BIPM (Paris). The frequencies of the line centres of hyperfine structure (hfs) components o, p, q, r of the R (127) 11-5 absorption line of ¹²⁷I₂ measured directly by beat frequency measurement are presented. Taking into consideration that the measured laser has a mean frequency offset of -22 kHz for hfs components (a-n), the following frequency differences of the components o, p, q, r with reference to the component i of the reference laser INVAR 1 have been obtained: δν_oi = (-263,187 ± 0,01) MHz δν_qi = (-292,689 ± 0,05) MHz δν_pi = (-290,271 ± 0,05) MHz δν_ri = (-320,720 ± 0,01) MHz. The He-Ne/I₂ lasers have been used for testing the single-frequency-stabilized lasers.