I have never seen a product review for penny sleeves, so I wanted to do one. These standard sleeves get overlooked, but they are essential for any new sports card collector. They are made for base cards or common cards. This includes sports cards, magic the gathering, Yu-gi-oh and pokemon cards.
Common cards typically have a 20 to 25 point thickness. Relic cards typically are thicker. I do not recommend using these for relic cards, mat cards, triple threads, etc because they do not fit cleanly into these sleeves. Use thicker sleeves for those like the 130 pt sleeves (http://youtu.be/viuZEAkhngo).
Protect your cards and protect your investment.
Here are some links to buy them online. You local baseball card shop should have them. They cost around $1 for pack of 100.