[INFINIBAR] Magnetic Spacers only available for PB6 & PB12?

The INFINIBAR PB3 is taller than the PB6 and PB12 because the same components must be packed into a smaller 1-foot form factor. As such, the PB6 and PB12 could be made slimmer to reduce the thickness and weight. The magnetic spacers bring the apertures of each lamp to the same height when used along with magnetic spacers.