There's No Such Animal..............<br /><br />There's 1 7/8ths"....<br /> 2"......<br /> 2 5/16ths".......<br /><br />A 2" coupler Will ride on a 1 7/8ths" ball......<br />It will Not come Off, But will Rattle abit......The odd thing is that the manual calls for a 2 1/2" ball.