A lot of pianos have a hole drilled in the flange to receive the tail end of the spring either right or left ( if no hole drilled any spring will do ).
Piano Hammer 'Butt' Springs for Upright Pianos 12 springs or a Full Set
Piano Hammer 'Butt' Springs - 12 Springs for Upright Pianos
70pcs Piano Spring Accessories Piano Hammer Butt Springs Upright
90pcs/set Musical Instrument Piano Hammer Butt Springs
