This is what 2A Armament says :
 
 
The 2A Armament™ Titanium takedown pin set features a through drilled design for maximum weight savings in a standard .250 pin size. The head of each pin also incorporates a pocketed feature to reduce weight.  Using certified U.S.A. 6AL-4V Titanium these pins weigh in at 0.18 oz total for both pins combined. The 2A Armament titanium takedown pins are aesthetically pleasing on both our BALIOS and BALIOS-lite receiver sets, as well as other vendors product. These feature a black ion bond for a dark matte finish.

Features:

    "Mil-Spec" .250 size
    Made from U.S.A. grade 5 6AL-4V titanium
    Weight: 0.18 oz combined
    Through drilled for weight reduction
    Pocketed design
    Black Ion Bond matte finish
    Product of the great state of Idaho, MADE IN THE U.S.A.
    SKU (2A-TI-TDPBLK)