They use very poorly made mushroom pins. Generally they're quite easy, like picking a regular spooled lock only with much sloppier tolerances... although sometimes they don't even go into false. But you do get the odd one which is a complete pain, and nobody knows why. My advice to you is, collect more locks. It's not good for your confidence when your only lock as a beginner is one which is supposed to be easy, and in reality, genuinely isn't.
Seriously, they can be nightmares. I've been picking for years and have a tri cirlce padlock that I've still never picked. It won't SPP, it won't rake, it doesn't even have a crazy bitting and the key works fine. Talk about frustrating... but hey, that's the way it goes sometimes.
)