Polypropylene pucks are used to assist in the filling and sealing of child resistant sprayers in two sizes. The child resistant sprayers are inserted into the pucks then filled. Pucks will keep the child resistant sprayers in place while being sealed by hand or using a press assembly machine and include four drainage holes in case of overfilling. These pucks are not interchangeable; you must purchase the corresponding puck for each size of child resistant sprayers you would like to fill. Puck colors may vary.