Adam,
I got a very similar one from Lee Valley but have never been able to make them work very well. I do not know what if any differences there are in the different lens supplied but mine do not seem to remain rigid in the lens holder. Also you are suppose to be able to combine various strengths to get more magnification. The directions that came with mine are typical of products from overseas with little to no useful information for the user. If you have any suggestions on how you have found them to work, they would be appreciated. Thanks.
elkhorne