The 140K did not come with a peep sight but the 140B did. It took a S130 peep. The mounting hole pattern is the same for many Mossberg mounting peeps starting with the #4 (S-104). The Lyman 57M or later 57MS, Parker-Hale PH-16D, Marble-Gross Moss440, some Redfield 70/75/80, but not the Mossberg S108.