Don't listen to the folks who tell you the aluminum blocks are too cheap to be any good. It's obvious they've never used any Lee molds. 36 years ago, I bought my .54 Improved Minie Ball mold, the twin to the .50 cal mold sold here. I still use it today, and it still casts perfect minie balls for my rifles. I also have several other molds for round balls, and they are also sturdy and durable. Aluminum heats up quicker, and maintains temperature throughout a casting session. Whether the Lee mold, or that $85 iron mold, both cast equivalent (excellent) quality balls/bullets.
Pros: Precision made. Casts quality projectile. Heats up to casting temp quicker than iron moldblocks.
Cons: If you cannot maintain a casting rhythm, and need to stop during a casting session, the aluminum blocks cood down quicker than iron.
This review was written in the old system and had content requirements that are different than reviews written today.