System for a dispenser of roll material, the system comprising an end plug of an exchangeable roll of material and a retention mechanism for retaining the end plug, wherein - the at least one retention mechanism is mountable in a housing of the dispenser; - the at least one retention mechanism is designed to hold the end plug in a seating region; - the end plug comprises a fitting portion dimensioned to fit into a hollow core of the roll of material, and a bearing pin extending from the fitting portion; - the bearing pin being provided with at least two portions, a first portion with a first diameter, and a second portion with a second diameter, the second diameter being smaller than the first diameter; the retention mechanism comprising: - an insertion slot extending between a receiving end and the seating region for inserting the bearing pin of the end plug; - a pin discriminator means; and - a loading ramp extending in insertion direction to the receiving end of the insertion slot is dimensioned to support the bearing pin before entering the receiving end of the insertion slot and has a slope going up in the insertion direction; characterized in that - the pin discriminator means is provided at least at the receiving end of the insertion slot and narrows the receiving end of the insertion slot such that wrong bearing pins which have any outer diameter in the second portion exceeding the second diameter cannot even enter the receiving slot and a slide back down the loading ramp; - a rejecting slot extending from the seating region is dimensioned such to receive other wrong end plugs with a bearing pin with any diameter of the first portion which is smaller than the first diameter; and wherein - the loading ramp is provided with a positioning surface which is perpendicular to the support surface of the loading ramp and essentially parallel to the insertion direction, and the positioning surface comprises a rib extending from the support surface of the loading ramp and being arranged to abut during the insertion of an exchangeable roll of material against a step portion between the first portion and the second portion of the bearing pin. - the at least one retention mechanism is mountable in a housing of the dispenser; - the at least one retention mechanism is designed to hold the end plug in a seating region; - the end plug comprises a fitting portion dimensioned to fit into a hollow core of the roll of material, and a bearing pin extending from the fitting portion; - the bearing pin being provided with at least two portions, a first portion with a first diameter, and a second portion with a second diameter, the second diameter being smaller than the first diameter; - an insertion slot extending between a receiving end and the seating region for inserting the bearing pin of the end plug; - a pin discriminator means; and - a loading ramp extending in insertion direction to the receiving end of the insertion slot is dimensioned to support the bearing pin before entering the receiving end of the insertion slot and has a slope going up in the insertion direction; - the pin discriminator means is provided at least at the receiving end of the insertion slot and narrows the receiving end of the insertion slot such that wrong bearing pins which have any outer diameter in the second portion exceeding the second diameter cannot even enter the receiving slot and a slide back down the loading ramp; - a rejecting slot extending from the seating region is dimensioned such to receive other wrong end plugs with a bearing pin with any diameter of the first portion which is smaller than the first diameter; and wherein - the loading ramp is provided with a positioning surface which is perpendicular to the support surface of the loading ramp and essentially parallel to the insertion direction, and the positioning surface comprises a rib extending from the support surface of the loading ramp and being arranged to abut during the insertion of an exchangeable roll of material against a step portion between the first portion and the second portion of the bearing pin.