Spring bar conundrum: what’s the benefit here?

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These two spring bars are advertised as being for pierced lugs. They have vey similar specifications, but one is shoulderless on both sides, whereas one has a single shoulder on one side:



My question: what’s the benefit having one side with a single shoulder? Easier to remove?
 
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These two spring bars are advertised as being for pierced lugs. They have vey similar specifications, but one is shoulderless on both sides, whereas one has a single shoulder on one side:



My question: what’s the benefit having one side with a single shoulder? Easier to remove?
That would be my guess.
 
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Could it be that the shoulder side is sprung and the other not, making the bar stronger??
 
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I believe they’re both sprung. Could be wrong though.
 
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I used to hate springbars that were shoulderless (like the Seiko OEM fat springbars of the SKX/Monster); but now I love them. They are much harder to remove (even with a decent springbar tool remover tool); but that's the whole point. I feel much more secure and confident that the springbar will remain there if anything gets caught in it's way.
 
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Both sections are sprung, it's not a shoulder. At least that's the case on the ones I've come across.
 
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I always assumed it was to allow them to be shortened by a greater amount. If a longer pin of the same diameter was used it wouldn’t be as secure. Equally a wider pin can’t be used for the full length of the sprung part as it won’t fit the lug hole.
No idea if that’s the actual answer though.
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