I purchased an assorted bag of LEGO Technic pieces. There are pieces with axle holes, but what puzzles me is that the holes are different from what I am familiar with.

  1. There's a piece with an hourglass-shaped hole (center of photo). What is the purpose of this shape?

  2. There's a piece with an hourglass-shaped hole, but with two thin tabs (left in photo). What is the purpose of this shape?

I'm familiar with the normal round hole, in which an axle can rotate freely, and the "plus" shaped hole, found in cogs etc., that grip an axle so the piece doesn't slide along the axle. But these two are new to me, and their purpose isn't obvious.

enter image description here

  • I read your question and really can not understand what you are asking. I suggest you to add some images to illustrate because many others will find this explanations confusing but might give you an answer if you illustrate. Commented Jul 3, 2014 at 10:25
  • I said I will upload a photo. The mobile app can't do that. Can you wait a few hours? Commented Jul 3, 2014 at 10:27
  • 1
    @TorbenGundtofte-Bruun: I've added a photo to illustrate (4), based on your description. Is that what you had in mind?
    – Kramii
    Commented Jul 3, 2014 at 11:20
  • 1
    Thank you @Kramii, that's right! I've swapped it for my own now. Commented Jul 3, 2014 at 11:30
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    See this answer for more info: bricks.stackexchange.com/a/6462/5687
    – UlfR
    Commented Jun 30, 2015 at 5:52

1 Answer 1


These are 3 different versions one the same shape / function that fit over axle.

  • The right one is the oldest from the 80

  • The left one came next

  • The middle one came after that.

  • To make it more confusing, lego is now back producing the right shape again

What I can remember had the original one a lot of clutch power and was hard to be removed.

Personal I think the left one had some problems with manufacturing, due to the small tabs.

I believe the middle one broke easily.

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