Commonly called yo-yo's at the Hydro store. The correct name for these yo-yo's is, spring balancer or tool positioner. You can buy them preset or you can buy the adjustable type (recommended). These units, when adjusted properly neutralizes the weight of the light and only takes very little effort to raise and lower them. There are two factors to take into consideration, the weight of the light and the length of throw, how far it will raise up and down. Remember you are using two balancers so each balancer must handle 1/2 the weight of the light.
ebay link

AERO-MOTIVE TOOL COMPANY GM-31 1-10 LB TOOL POSITIONER - eBay (item 360127670907 end time Feb-27-09 12:02:08 PST)
ebay link

SunRise Reflector Hanging System - eBay (item 110346237238 end time Mar-04-09 10:11:45 PST)


I have spent a bit of time looking for deals and these would be the no brainer

SunRise Reflector Hanging System - eBay (item 110346237238 end time Mar-04-09 10:11:45 PST)

This kind you raise and lower like the blinds in your house

Grow Light Hanger move up/down Hydroponic FREE SHIPPING - eBay (item 120373541513 end time Feb-11-09 02:49:27 PST)

I am not promoting Sunset Hydro but, it is where I buy my supplements. Always in stock and almost always free shipping.

Hello,
I thought I would put some more information on these very handy, reflector hanging systems. I am showing you how I use them in my room. I personally wouldn't grow with out them. They make my time in the grow room much easier. You simply raise and lower your lights to the height you want, with little effort.
The first pic is the overall shot of how they are used in my room.
Attachment 18592
The next pic is how they attach at the reflector. Most light hoods come with the bracket you see. You simply tie a strong knot to the bracket that is attached to the reflector.
Attachment 18593
This is a close up of the actual device that controls the tension of the spring. You can see there is a wing nut to tighten or loosen, depending on the weight of you lights.
Attachment 18596
This is how I attached them at the top, this method was overkill but I had these eye bolts on hand. All you really need is a strong J-hook to screw into a roof truss or something very sturdy.
Attachment 18602
I hope this helps you sometime, and makes the time you spend with your plants more enjoyable.
Here is another link to purchase these little gems. http://www.hydrofarm.com/pb_detail.php?itemid=3780
GSR

__________________
Just in case you are wondering what The Emerald Triangle is.
http://en.wikipedia.org/wiki/Emerald_Triangle


Check out my latest project
http://www.greenpassion.org/f16/south-emerald-triangle-7780/

I was looking for something else and this caught my eye.
4 YoYo Flexi-Adjust Grow light Reflector hangers MH HPS - eBay (item 270339733816 end time Feb-08-09 21:10:00 PST)