as long as you take your time and give it a little shake with every round and watch and make sure the next round slides down then they are great, with practice you can load a magazine in under 30 seconds.
BUT,,.... some things I have found
1) even though the hopper will hold 50 rnds, ONLY put 25 in at a time and you will be much happier.
2) make sure the next round slides down into the turning style properly, slow and steady here is the rule or you will dent the casing.