Can anybody recommend a good lens protector for shooting? I want to shoot close to the street with moving objects and I am afraid a stone might crack the lens. What kind of filter can I attach that will not effect the picture whatsoever. Someone mentioned a polarizing filter but it seems like that might change the picture slightly. Does anybody have any good suggestions? Thanks for your help!!!

A high quality UV filter is often used to protect the front element. Look for one that is coated to minimize internal reflections.

Be aware that dust on a filter can become visible in the image so you have to take care to keep it clean.

Don is right. The first things I bought for my three GL2s were UV filters that live on the cameras at all times. It's the ol' "an ounce of prevention being worth a pound of cure".

I would much rather have to buy a new filter than a new lens!

Thanks guys for all your help. Can you recommend one to get? It seems there are so many and if you are having success with the ones you have I will probably get some of those. Thanks!

if you are having success
It is difficult to measure success in protecting the lens against flying pebbles. I bought a simple UV filter and the picture in my XM2 did not degrade. At least I did not notice degradation. For the best in filters go shopping for Tiffen: http://www.bhphotovideo.com/c/product/533194-REG/Tiffen_58HTDUC_58mm_Digital_HT_High.html

But I am using a less expensive brand.