The finest you will find on the market is not a base it is actually a reduction with no added salt just a stock reduced about 90%. CulinArte' Bonewerks
The have a glace de veau, mirepoix, porc, d'agneau, poulet, homard, and poisson. Exceptional one and all.
Their premade demi-glace is exceptional also.
Bonewerks™ CulinArte'**/**Glaces, Demi-Glaces, Sauces & More / Welcome!
Hands down the best premade I have ever had and I was a saucier for 10 years in a major hotel- the stuff rocks!