These look clever

[HardRockCamaro]

Shows you at a glance if the bolt is correctly tightened:

http://www.smartbolts.com/p_precision.htm\" target=\"_blank\" rel=\"nofollow\">http://www.smartbolts.com/p_precision.htm

[Ponti]

I bet they won't be cheap, also only good if you can get a clear look at the head to check the colour.

[philoldsmobile]

skeptical... for that to work it would assume you always need to be tightend to the same tension..

[HardRockCamaro]

I thought I read somewhere that different sizes of bolts are designed for different amounts of torque, hence why you use one size over another?

I could be confused though...

[Titsy]

No one has spotted the obvious... How in hel to you look at the tit while tightinging the bolt up with a rachet?

[EDGE]

thats EXACTLY what I thought when I first saw it... unless you're using a spanner ???  

Or indeed one of those hollow sockets you're meant to use while tigthening bolts on a threaded bar...

[HardRockCamaro]

I think the idea is that they're supposed to show you if they've loosened as opposed to act like a torque wrench?  Although you could tighten, check, tighten etc I suppose?

Bit like those plastic things they stick on truck wheel nuts to show if they're rotated?