I used 3157 bulbs. They have 2 filaments, and are the newer 1157. They have wires you can bend out. I bent out all thewires there are 2 on each side. Bend them so they stick perpendicular to the bulb. I them put the bulbs in a circle. They just fit. Solder all the wires on one side and all the wires on the other side. Hook a heavy wire to each group of wires. It comes out to 10 amps.
Each bulb should look like thisl _0_
Works great, no jig needed or holder when it is finished.
I paid $7.00 for the box of bulbs.
My packs are performing much better since I started using this.