I see you have already gotten answers. You can also make riser blocks, rather than buying, probably a search will explain how.
Rather than just ask questions tho, try to find the answer on your own. This will have a number of benefits. You will run across things that interest you, possibly not even connected with what you're searching for. You will find what you're interested in. Less people will think you're ignorant.
And, if you don't find what you're looking for, say you can't find it, and ask. Remember, google is your friend. I for one will go the extra step to try and help someone who I think has tried to help himself first; otherwise I rather feel like someone is trying to get me to do their homework for them. But don't be afraid to ask if you can't find the answer on your own.
Oh, just ask. A lot of times hours or days can be saved by getting the meat of the issue from someone who knows, rather than filtering thru the vast minutia of worthless info on the net, plus people here will MOSTLY explain it in a way that makes sense, rather than in "technical terms". Then, after getting answers that are understandable, if you choose to search you may find that much of what you now read makes a lot more sense, since you grasp enough new knowledge to interpret what you read. I didn't think you were ignorant, and neither do most of the other posters in this forum. Shoot sometimes I ask questions I already know the answers to, just to see if the others have a different or better way of doing something.
He is no fool who gives what he cannot keep to gain what he cannot lose
If you cannot stand behind our troops, (and I understand, no judgement here), then please stand in front of them, remember, they're willing to stand in front of you!