Are you considering a balance transfer? If so, what do you really know about them? Chances are that you’re considering that balance transfer because you know it’s a way to save money compared to your current higher interest rates. You probably also know that many credit cards, like the Citibank Silver credit card, offer special balance transfer rates that are only available for a limited time.

Knowing that your balance transfer rate will eventually increase if you don’t pay it off in full isn’t all you need to know though. Here are three things you might not already know about balance transfers, but things which should play a role in your decision about whether or not a balance transfer is really the right move for you.

1. You might be charged a fee for transferring a balance to a new credit card.

With saving money likely being a top priority in your choice to initiate a balance transfer, you should probably pay attention to the fees. Balance transfer fees usually come in one of two varieties: a flat fee or a percentage of the balance transferred.

Why is it important to know about balance transfer fees before starting a balance transfer? Well, if the idea is to save money you’ll want to find out up front what the transfer will cost you so you can be sure the overall savings are still worthwhile for that particular credit card.

2. You might not be able to transfer your full balance.

If you want to use balance transfers as a debt consolidation tactic, you might be hoping that you can transfer multiple balances to a single new credit card. You might be unpleasantly surprised though. Not only might your new balance transfer card not approve multiple balances to be transferred, but you might not even be able to transfer the full balance from one current credit card. You could only be approved for a portion of the balance.

On the flip side, balance transfer cards will often have a minimum balance that you have to transfer — for example, you might have to transfer at least $500, so you won’t be able to use a balance transfer to save money on a $400 debt.

3. Your balance transfer might eliminate your interest free days.

Interest free days on purchases are generally contingent upon paying off your balance in full during the previous statement period. That includes your balance transfers. If you plan to use the new credit card for purchases in addition to a balance transfer, you probably won’t be eligible for any interest free days until that balance transfer is completely paid off.

Why is this important? Knowing this and your usual spending habits, you’ll be able to find a balance transfer card that suits your needs. For example, if you make a lot of purchases and plan to do so with the new balance transfer credit card, you know to look for a card with a low purchase rate.

None of this information is meant to warn you to stay away from balance transfer credit cards. It’s about knowing all of the facts up front so you can choose the right credit card when you’re ready for a balance transfer. Just remember to that exact details vary from one card to the next, so it’s important to review the credit card terms carefully before applying.