David, the flat area ["ball bearing"] you point out is the old part that your new part will replace, they're identical, need to remove it as shown in DG's pic, although you don't need to fabricate a special puller like he did, just get under the flange edge that sits atop the mast jacket with a stiff putty knife and work around gently tapping it up until you can get hold of it, pulls right out with the horn wire attached to the back of it
Bill
