This is a pair of invert roller pulleys with new high-tech slide bushes for using on any invert/ cord roller spearguns. These can take spectra or dyneema lines with a diameter up to 3 mm.
The external component, which houses the line, is made of black hard polymer; the inner bushing, which is the heart of the pulley, is made with high-tech materials and machined to ensure excellent smoothness.
They have a very low coefficient of friction on the axle and at the same time good wear resistance.
Size as per attached picture. Fits on your choice of length in 6mm diameter axle.