To attach these to older walkers, you will have to drill two holes in the walkers. The instructions detail this procedure.
See the accompanying chart for model numbers and sizes.
The above image shows the EA2 Extensor Assist Center Pad and the PS2H Pelvic Stabilizer side pads on a W2B walker. The left image shows the EA2 Extensor Assist Center Pad on a W2B walker.