(Your guess is as good as mine for why I like so nervous about touching it!)
INTERFERING IN A GOOD WAY
If you don't know the story behind these, rather than a machined steel tube, the Laser Speed Lights have an Aluminium Tube with a steel tooth section set with an interference fit. The far lighter aluminium tube gives the significant weight savings.
The downside of this is that in theory the tubes and as such threads are prone to damage more easily but truth be told mine which are mainly thrown at pure ice routes have held up fine but they're stored safely in Black Diamonds fantastic Screw-Up sleeves when note in use. Climbing mixed alpine routes with them, rubbing up against granite might cause a bit more trouble although I've not heard of any evidence of this.
Oh and they're a bit more expensive (and don't come in stubby 10cm lengths).
The same style of Aluminium tube with steel teeth, they saved further weight with steel wire handles and so their 16cm screws are 81g compared to the 100g for the Petzl Speed Light a further 19% saving - a WHOPPING great 45% saving on their own Express Ice Screws!
Also Black Diamond's Ultralights are GREEN! Which if you see in the photo of me climbing above is a serious consideration!
So in conclusion if you've got the pocket money and you're climbing Ice and are buying a rack or have an array of old blunt steel screws buy Aluminium, you won't regret it, it makes your Ice Rack feel like a Sport Climbing rack in comparison to that you'd need on a Big Wall!
- Pete -