XRAY - Model racing cars

Which one best to use?

Some say SpecR because of the mounting rings.

Xray: do they come with the flat spot pins or do I have to buy these seperately?

SpecR only available in 50mm?

XRay available in 50mm and 52mm.

Do I have to use shrinktube with both of them?

On the XRay leaflet on these drive shaft it is not mentionend as so.

I use Reflex Racing.
They do a 51mm and 52mm, use pins with rings like the Spec-R, but are better quality.

I still use thin transparent heatshrink on them no matter who's I use.

Thanks for the info.
I'm gonna look in to the ones from Reflex Racing.

That would be these:?
http://www.reflexracing.net/RSD-XRAY-SP ... _1673.html
and
http://www.reflexracing.net/RSD-XRAY-SP ... _1674.html

Aren't they the same as the ones on the Spec-R website?

RSD CVJ: when to use narrow ones and when to use the others?

The XRay CVJ leaflet and the X4 manual say different things. There is a discrepancy!
On the leaflet it says foam racing use 50mm or rubber racing use 52mm.

In the manual it says:"50mm shafts are recommended for small-medium tight asphalt tracks."
In the manual it says:"52mm shafts are recommended for carpet and large asphalt tracks."
In other words, in the manual there is no talk of foam or rubber racing, so no emphasis on the sort of tyres. In the manual the amphasis lays in the sort of track.

Also in the manual:"Longer drive shafts (52mm) make the car easier to drive because they
give more traction and better stability, mainly in chicanes. However, the
car will understeer more than with shorter (50mm) shafts which give a lot
of steering and impart aggression to the car."

I am somewhat torn as to use which shaft under which conditions...... (I mean the length).

Please elaborate.

Club conditions are: short track, low grip.
Nats tracks are various: long tracks and short tracks, low to medium grip.

Which shrink tube?
How many mm?

As I understand it, better not use the Spec-R ones.
As I understand it, better use the RSD ones and not the XRay ones?
Why is that?
Some say because of the retainers that are safer. No screws turning loose during racing, or so......
Other arguments?