Review on Sylvania 20318 Compact Fluorescent 4 Pin Single Tube 4100K, 13-watt: Efficient Lighting Solution for Any Space by Veronica Toledo

With 1 necessary and 1 additional modification, your old C3 lamp will work again. First you need to shave off the 2 bumps on one side of the plastic base - the original bulb has a bump in the center that slides into the recess of the bulb (see image). The replacement Sylvania bulb fits without scraping the two ribs if you push it in there, but the bulb will tilt towards the front of the lens. I used a utility knife and it took me a few minutes to shave the bumps. 2nd and semi optional, you need to make a spacer to fill the gap at the top because this bulb is shorter than the original. It's exactly 9/16 inches shorter. So I used a hacksaw to cut a 9/16 inch piece off the hockey stick to place over the rubber pouch holding the top of the lightbulb (2nd picture). Affectionate like a beetle.