This strap is working out really well for me. I attached it to my EOS Rebel XSI camera and have never since felt the need to take it off for any reason.
Attaching the strap:
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The strap attaches to the camera from the right shoulder strap loop and the tripod mount on the bottom. Once attached, you can still use a shoulder strap with it. There is a loop on the plastic component which screws on to the tripod mount. You attach one end of the shoulder strap to that, and the other end to the left loop on the camera.
You can still mount the whole thing on a tripod as well because the bottom component has a place for attaching the tripod. In short, it doesn't take away any of the existing attachment points which it now occupies.
How the strap feels and works:
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The feel of it in my hand is really comfortable. The exterior looks like black leather and the interior has a rubbery texture so it is slip resistant.
It is very effortless to hold the camera in your hand with the aid of the strap. You just have to curl your fingers around the side of the camera and the strap keeps it secure in your hand. You don't need to grip it between your fingers and your thumb as you would if you didn't have this strap. This allows you to free up your thumb firstly, and secondly it allows more dexterity on your index finger for controlling the shutter release and the wheel. Since your hand is pretty much strapped on, the iso select button is harder to reach.
While the thumb becomes free to control the arrow keys and other buttons, it becomes quite easy to access all those buttons with one hand while your other hand becomes free to control the zoom/focus on the lens.
I can straighten my fingers, palm facing down, and let the camera hang from the strap vertically down while being supported from the strap going around the back of my hand without fear of the camera slipping and falling at all. It is slip resistant and feels securely fastened to my hand as if it was an extension of my hand.
I initially had a tendency to make the strap really tight and barely enough room to slip my hand in there and give me a snug tight fit. This in turn caused the thing to be uncomfortable as I was bending the wrist and overextending my thumb to reach the buttons. I find it much more comfortable if I keep it a little loose so that I can slip my hand easily into it and there's some room for my fingers and thumb to move, some breathing space if you will..
The construction of the product doesn't feel cheap or low quality. The black leather exterior actually looks quite nice. I did have one issue with it however. The plastic component which attaches to the tripod mount has a rubber surface which comes in contact with the bottom surface of the camera. If you screw on the item to the tripod mount too tight, the rubber contact surface tends to come off and stick to the camera, which is kind of low-quality.
Conclusion:
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I think this strap is an absolute must-have. It makes the SLR very effortless to operate with only one hand. For someone who will want to carry the camera in their hand for extended periods of time, for example going for a tour of a museum/zoo etc.. this would be very helpful.
You're essentially buying yourself some insurance with this strap and is not really that bad on a 0+ camera.
Average Rating:

Brand: Opteka
Model: OPT-GS
Product Description:
The Opteka padded camera grip wraps around the hand, and is designed to stabilize a camera or camcorder when shooting, and to alleviate fatigue during extended sessions of photography or videography. Compatible with all Canon, Nikon, Sony, Olympus, Pentax, and Samsung DSLR cameras that feature a standard 1/4"-20 tripod socket .
Features:
- Compatible with all Canon, Nikon, Sony, Olympus, Pentax, and Samsung SLR cameras that feature a standard 1/4"-20 tripod socket
- Padded professional quality grip strap
- Designed to stabilize a camera when shooting
- Alleviates fatigue during extended sessions
Available at Amazon
List Price: USD 29.95
Lowest New Price: USD 9.95
Customer Reviews

fine
its work very well the only thing is if you want to shoot vertically this is not gonna work for you if you have cameras with battery grip

Strap
Fits good and does it's job. It does take some of the weight of your hands while holding the camera. My only regret is I should of purchased two..

Very "Handy"
Don't know if I'm using it "right" but I do know that it seems more convenient to me to pass the strap from the camera across the back of my hand and carry the camera that way while being pretty much always ready to swing the camera up to take a quick shot instead of having it dangling from a neck strap and bouncing on my belly. By the way, I'm using it with a Canon Rebel T1I.