A staple claim in Chinese skincare ads. Dermatologically pores cannot truly be 'shrunk', only made to appear smaller — but 收毛孔 dominates marketing copy alongside 美白 (whitening) and 抗老 (anti-aging).
register
Colloquial / marketing register. 收 here is a verb meaning 'tighten / draw in'. The fuller technical phrase is 收缩毛孔 shōusuō máokǒng.