I read several comments like what it was not compatible with D3100. ERROR !!! Do not confuse body and lens ^^
In the description there has marked it as a 52mm diameter, so perfectly compatible on the 18-55mm sold in the kit.
In this case, APSC sensor, wide angle 18mm becomes 12mm, very interesting. But what stuck me most is the macro part. I did not want to put 400 in a macro lens and for the price, it is a small stone jewelry. Certainly it will be advisable to use in good condition for exposure, but to take 15 retail copies on a marriage for me (covenant, shows, ect ...) it is the perfect gadget !!!
I really recommend it !!!