Thanks for the tip off Mike...
With the fast approaching mercury lamp ban,
Sylvania have launched a retrofit ceramic metal halide lamp for use on mercury control gear. The lamps come in three sizes with ES caps, are elliptical coated lamps, and have the appearance of a mercury lamp crossed with a domestic CFL, given the presence of a housing which contains some electronic circuitry. Here are some comparisons:
80W MBFU (3600Lm) -> 55W Relumina (4500Lm)
125W MBFU (6200Lm) -> 85W Relumina (7500Lm)
250W MBFU (12700Lm) -> 170W Relumina (15000Lm)
The smaller Relumina lamps are 62mm diameter by 178mm length, compared with 71/76mm diameter and 155/173mm length for mercury lamps. The large Relumina lamp is 87mm diameter by 228mm length, compared with 91mm diameter and 226mm length. Hence, even though they have a strange shape due to the integral circuitry, their size is similar.
No doubt these lamps cost a lot more than mercury lamps, but Sylvania suggest that they should pay back their cost within 6000 hours of use.