A.T. Robertson Commentary Revelation 16:21

"And great hail, [every stone] about the weight of a talent, cometh down out of heaven upon men: and men blasphemed God because of the plague of the hail; for the plague thereof is exceeding great." — Revelation 16:21 (ASV)

Hail (χαλαζα). As in 8:17; 11:19.

Every stone about the weight of a talent (ως ταλαντιαια). Old adjective (from ταλαντον), here only in N.T., but in Polybius and Josephus. See Ex 9:24 for the great hail in Egypt and also Jos 10:11; Isaiah 28:2; Ezekiel 38:22 for hail as the symbol of God's wrath. In the LXX a ταλαντον ranged in weight from 108 to 130 pounds.

Because of the plague of hail (εκ της πληγης της χαλαζης). "As a result of the plague of hail." This punishment had the same effect as in verses 9,11.

Exceeding great (Μεγαλη--σφροδρα). Emphatic positions at ends of the clause (great--exceedingly).