Adding the right reflector to your lamp can optimize the space your light covers while providing the best light efficiency for your plants. There are many different kinds of reflectors available; open M, winged, dish, air cooled etc. It is impossible to suggest one over the other as they all depend on the style that best suits your growing needs, which type of bulb you match with, and your budget.
When looking for the right reflector for you, remember that white or metal hammertone finish will best reflect the light. Then, match the size of reflector by the area you wish to reflect light into (if you only have a small grow area, you may not require a 1000w light and large reflector).
One of the most popular and best results for reflectors has been found from the Hydrosun Horizontal.