I agree with you , great quality, quite heavy though, i think filled with sand.
I also have the porta aim ,build quality is fantastic, but i find it a little bit too high for my home setup, quality though for the cost
On the subject of bags though I have a Caldwell 'universal' rear bag and a little Protektor 7A front bag. Both filled with plastic pellets from eBay - I wouldn't personally use anything else now. Dust free, inert, doesn't attract moisture or rodents, nice weight.