An agricultural baler (10) includes a main bale chamber (26) having a pair of opposed side walls (40), with each said side wall (40) including a plunger slot arrangement defining a plunger slot (42). A pair of plunger slot rails (48) are positioned in each plunger slot (42), including a top rail (48A) positioned at a top of a respective plunger slot (42) and a bottom rail (48B) positioned at a bottom of a respective plunger slot (42). A plunger (30) is reciprocally disposed within the main bale chamber (26). The plunger (30) includes a pair of opposed sides (46) and at least one roller (44) extending laterally outward from each side (46), with each roller (44) being positioned within a respective plunger slot (42). The baler is characterized by a pair of plunger slot cover assemblies (52), with each cover assembly (52) being associated with a respective plunger slot (42) and having an upper cover (52A) and a lower cover (52B).
