A unit (100) for filling containers (2) with products (1), in particular pharmaceutical products (1), includes a hopper (3,3a) containing a mass of products (1) in bulk, conveying means (5,6) aimed at feeding the products (1) leaving the hopper (3) along a predetermined path (P) up to a station (SR), where the containers (2) are filled with the products (1). The containers (2) are fed to the filling station (SR) by transporting means (4,C). A checking station (SC) for checking the products (1) is situated along the path (P) upstream of the filling station (SR). The conveying means (5,6) include first means (51,52,53) consisting of vibrating planes and second conveying means (6). The second conveying means (6) are situated at the checking station (SC) between the conveying vibrating planes means (51,52,53) and the filling station (SR). The second conveying means (6) are equipped with holding means (65) for holding single products (1) thus forming, on the second conveying means (6), a series of single products (1), spaced apart and moving forward to the filling station (SR) along a portion of the path (P).