Albert Barnes on 2 Corinthians 11:18

Seeing that many glory, etc. The false teachers in Corinth. They boasted of their birth, rank, natural endowments, eloquence, etc. 2Cor 11:22. Comp. Php 3:3,4.

I will glory also. I also will boast of my endowments, which, though somewhat different, yet pertain in the main to the flesh also. 2Cor 11:23, seq. His endowments in the flesh, or what he had to boast of pertaining to the flesh, related not so much to birth and rank, though not inferior to them in these, but to what the flesh had endured--to stripes and imprisonments, and hunger and peril. This is an exceedingly delicate and happy turn given to the whole subject.

(f) "Seeing that many" Php 3:3,4, 1Cor 4:10