A GZ10 cap is very similar to the GU10, but should not be used in a GU10 lamp holder. This is because the GZ10 is always a dichroic halogen lamp that dissipates its IR heat through the back of the lamp, and therefore has very specific heat dissipation requirements. Theoretically the GZ10 should not physically fit into a GU10 lamp holder, because of the difference in tapered design. A GU10 can be used in a GZ10 socket, however. Care should be taken not to buy this cap or bulb unless a suitable receptor allowing for rear ventilation is available.
Dichroic or ‘Cool Beam’ GZ10.