5 1/2" Tubular Light Bulb with Standard Base, 40 watts. 

This is the one we use in the Large Light Kit for the Christmas Trees.

• Buy 1 - 4 and pay only $2.50 each
• Buy 5 - 24 and pay only $2.25 each
• Buy 25 - 49 and pay only $1.75 each
• Buy 50 - 99 and pay only $1.35 each
• Buy 100 or above and pay only $1.29 each