a pair of elements for providing slidable electrical contact therebetween wherein the contact surface of at least one of the elements comprises a plurality of contact portions and a plurality of depressed portions in between the contact portions so that wear particles which are generated between their contact surfaces as the elements are moved relative to each other are effectively swept from between the contact surfaces into the depressed portions where they are entrapped . such operation tends to maintain a low electrical resistance between the elements over many cycles of use .