I've tried the hand bands once for pull ups and toe to bar and I'm slipping off the bar. Do I need to make them tighter?
Don't give up after one try! HandBand Pro® original are very unlike gloves, pads, tape, and everything else out there, so there may be a just a bit of getting used to. The idea is to have as little interference with the bar as possible. They don't need to be very tight for them to be effective, but good hand placement on the bar helps, and so does a strong grip.
Are you putting just one finger through the finger slits?
Check out this video of how to wear them, and notice that only one finger should be used per band. If you put two fingers through, like your pointer and pinkie, you'll end up with a big gap between the palm of your hand and the grip, and that just won't do.
Sometimes it takes just a bit to get accustomed to how the handbands work and feel - especially if you're used to a raw grip. That being said, I wouldn't just throw them on and start competing in them. You need to work with them on a few workouts to get comfortable using them and they become second nature to you. For most people it doesn't take more than a week or so.
Another tip - be sure to wash your hands real well (with a non-moisturizing soap) to remove any oils or lotions from your hands before you put on your HandBand Pro® handbands. Our HBP Hand Sanitizer is a great way to quickly remove oily residue from your hands before your workout.