Rockwool Density?

Where i live i cant get the pre-made rockwool cubes i see that many people are using. So i thought ill make them myself out of Rockwool sheets. I can get Rockwool with the different densities 40kg/M3, 50kg/M3, 60kg/M3 and 80kg/M3. Which density is best to use for growing?
I searched the forum, but didnt find any info on it.
Thanks,
BtB

The pre-cubed/slab style rockwool used in hydro is high density and about 3" thick. I cut 2"x2"xH" cubes from high density slab.
I am now successfully using low density 2" rockwool that comes in a bale...which will last forever
With scissors I cut the cubes into 2"x2"x3" cubes and plant/clone with the grain, which is opposite from high density. I support the low density cubes with hydrorock.
In a cloning bin any proper size rock will do for supporting the low density rockwool..

Thanks mate. But what density is the "high" and "low" you are talking about? How many kg/m3?

I've never gotton that serious about the density of rockwool..
I get the hard slab from a hydro shop. It's about w6"xh3"xL36". It's firm enough not to bend easy.
The low density comes in a bale and is compressed like fibre glass home insulation. It is in fact more tedius to use.

Ok, maybe im focusing too much on the density. Ill probably get a little bit of each to try it out. Thanks alot for your input