A chemical mechanical polishing pad is provided containing a polishing layer having a polishing surface; and, an endpoint detection window; wherein the endpoint detection window comprises a reaction product of ingredients, comprising: an isocyanate terminated urethane prepolymer having 5.5 to 9.5 wt % unreacted NCO groups, wherein the isocyanate terminated urethane prepolymer is a reaction product of ingredients comprising: an aliphatic polyfunctional isocyanate; and, a prepolymer polyol; and, a curative system, comprising: 0 to 99 wt % of a difunctional curative; and, 1 to 100 wt % of an amine initiated polyol curative having at least one nitrogen atom per molecule and an average of at least three hydroxyl groups per molecule. Also provide are methods of making and using the chemical mechanical polishing pad.