I have the OP's scope from radio shack as well as the loop. BY FAR THE LOOP WORKS BEST. I bought mine at the hydro store and paid 4 times what it's worth. Fabric stores, coin shops, those places carry them. Mine has a led light on the under side that I never use but wtf..its there in case I need it.

The problem with the scopes is that you have to fix your head in one place and then adjust the lens. Nearly impossible to do when your plants are tall and you are trying to be careful not to damage anything. The loop works exactly opposite in that you fix the loop close to your eye and then move your head to focus. Much faster and more effective I found.

here is what you want: quick if you buy now you can have this one for .99. Too slow, but this is what you want: ebay loop