6 twist-in instrument panel light bulb lamp sockets.
Wedge bulb socket fits a 1/2" or 13mm diameter hole.
Compatible with these wedge bulbs: T10 W5W 147 152 158 159 161 168 184 192 193 194 259 280 285 447 464 555 558 585 655 656 657 906 912 1250 1251 1252 2450 2652 2921 2825
Fits: Most GM automobiles 1962-1985.