Insulation density question

Hi everyone Yes, I did a lot of searching and I couldn't really find an answer. I have seen Stuart say that we should use "mineral wool that has a density of around 50 kg/m3, or any type of fiberglass that has a density of about 30 kg/m3" in between inside and outside walls. But, manufacturers don't really publish density specs..... so outside of 703 (which I think is right in that range but I can't really source locally) what is the actual product I should look for from any of the leading vendors? Is there something I could get from Lowes or Home Depot that I can use between my inside out interior walls and my existing exterior walls? Or would John Sayers say don't worry too much about it and just put whatever in there as long as there is something in the cavity? Thanks in advance for your help.

One simple way to find out if you have the right density, is just to get some and weight it! For example, get a cubic meter of it, put it on your bathroom scales, and see how much it weighs... :) Or if a cubic meter costs too much, get a quarter of a cubic meter, weigh that and multiply by 4. Also, many manufacturers do provide those figures on their web sites, even if it isn't marked on the product packaging itself. And some building supplier web sites also list that in their product details on their web sites. - Stuart -