This is a multi-purpose special 3 in 1 insulator that works on T posts wood posts and some round posts. Great for high tensile steel wire insulated electric wire and will accept polywires and polyropes up to 3/8 in. (9.5 mm.) in diameterFeatures Fits both 1.25 lbs. & 1.33 lbs. T posts Insulator Material - High Density Polyethylene Attachment Position - Front Attachment Method - Snap on Nails/Screws Tie on Insulator Conductor Type - Polyrope Polywire Wire Fence Post Type - T Post/Wood Primary Color - White Dimension - 12 x 8 x 4 in. Item Weight - 1.5 lbs. 25 Pack - SKU: FMSP114