A low cost chain used to mount and suspend lightweight items.
The jacket used on double ended halogen bulbs serves the same purpose as the outer jacket of a JTT bulb. The jacket serves to protect against convectional currents, decrease surface temperature (when compared to the actual surface of the bulb), protect against exposure to oils and other surface contaminants and offer a small amount of protection against exposure to liquids.
Only used on High Output and Very High Output bulbs and was originally designed for cooler or freezer applications as well as outdoor use in extremely low temperature outdoor applications. The jacket on the outside of the bulb serves to insulate the bulb to prevent heat loss and to protect its surface from convection currents. Fluorescent bulbs have minimum starting temperatures and may not start when their temperature dips below that rating. Additionally, the performance of a fluorescent bulb is best when operated within a particular temperature range that is dependent upon the bulb's type.