I own a few bricks that contain a weight inside of them. 52g according to Lego.

What exactly is inside of these bricks that makes them heavy?


3 Answers 3


I did the unthinkable! ...I had to know.

I opened one of my two weighted bricks. One of the two ends has a glued-on cap that I've cut around using a utility knife.

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The piece of metal it contains fits almost perfectly in the cavity. I don't know metals but it has a rainbowish kind of sheen to it. Here's a close-up:

enter image description here

I'm now reassembling it back and super glueing it.

  • 19
    +1, for defacing a LEGO brick to provide an answer. I imagine you could weigh it to find it's mass.
    – Ambo100
    Commented Nov 22, 2011 at 16:35
  • 14
    Since when is defacing a LEGO brick worth +1? Heretic!
    – Joubarc
    Commented Dec 6, 2011 at 10:43
  • 3
    Makes sense that these would be galvanized steel since they were often used to balance the floating boats (e.g. 314, 4005, 4010, 4025, etc.) and could be reasonably expected to get wet and rust leaking out of the brick would look weird. Commented Feb 8, 2012 at 17:59
  • 3
    I literally gasped when I saw this. Commented Mar 1, 2012 at 15:40
  • 6
    I don't know whether to upvote this answer for being correct, or downvote for cutting lego bricks apart. This sort of experiment would never get past the ethics panel in my household. Commented Sep 11, 2015 at 18:31

I had two of these bricks in red, one is broken (one of the side-caps dropped off): there's just a piece of galvanized iron/steel in it.

My blocks were bought about 19 years ago, so maybe they changed the weight to an other/cheaper material in the meantime, but I don't think so.

  • 1
    This seems like it's correct. I'm going to do what Zhaph said and test it with a magnet.
    – Pubby
    Commented Oct 26, 2011 at 18:43
  • i'm not 100% sure it's iron/steel, but it pretty much looks like because it's galvanized, wich won't make much sense on other metals. i'm looking forward to the results of your magnet-test.
    – oezi
    Commented Oct 26, 2011 at 20:34

I'm fairly sure it's one or two pieces of iron, but I would need to check with someone who actually opened one. You can easily check that it's a ferrous metal if it attracts magnets.

  • 4
    Non-ferrous metals aren't magnetic... so a lack of attraction doesn't rule out the possibility of a metal being used ;) Commented Oct 26, 2011 at 15:17
  • 1
    Indeed, I oversimplified it, I guess I'll edit that in. But magnetic attraction will confirm it's a ferrous metal, and since I was pretty sure it's iron (as confirmed by oezi), I didn't want to bother thinking about other metals.
    – Joubarc
    Commented Oct 27, 2011 at 7:32
  • Lego magnets stick to them just fine. It takes two magnets to lift one brick.
    – Mark
    Commented Dec 14, 2017 at 7:13

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