It has a place for an on-board SD card (I'm not sure if it comes with it or not), but what you do is pull the card out of your trail cam, insert it in the 2nd SD slot and transfer the pics to the onbaord SD card. Then when you are all done checking trail cams, when you get back home, take the on-board SD card out of the view finder and plug it into your PC. OR you can even look at the pics in the field if you want to b/c there's a 4 inch screen that allows you to view them right then and there.
You can choose whether or not to delete pictures on the view finder or keep them on there. Same way with your SD card at your trail cams, when you transfer them, you can delete them (that way you don't have doubles) and clear your SD card on your cam. I always like putting SD cards in my cams that are BLANK b/c when I go and check it, I want the pic number to be exactly how many it's taken.
Hope this helps,,, I'm due to recieve mine this Friday and I'm excited about it. I actually saw one at Bass Pro and they were $80. The amazon.com one is exactly the same thing and it's new in package as well. Just $30 cheaper with free shippping. It's a small device, it looks bigger on the internet than what it really is. It can easily fit into your pocket on your pants or jacket.
BTW gfd.... my wife talked me into hitting up some black friday sales this past week and you wouldn't believe how many places had our famous WGI cams on sale for more than half what they were "worth" last year! haha Talk about junk. I have seen the Moultrie D55ir actually increase in price a little bit on Ebay, amazon and Bass pro.... I'm guessing they are finding out people like that model of cam. I do highly recommend my Moultrie D80.... very nice cam and take QUICK pics.
Good luck man,,, and let me know if you have any other questions about the view finder....
...I am not skilled to understand, what God has willed, what God has planned, I only know at His right hand, stands One who is my Savior....