Gainsborough kits use a different numbering system for bottom pins than used for replacement bottom pins. Refer lookup table below.

Pin # in kit	Refill pin #	Length
PB0	#0	4.0 mm
BP9	#1	4.5 mm
PB8	#2	5.0 mm
PB7	#3	5.5 mm
PB6	#4	6.0 mm
PB5	#5	6.5 mm
PB4	#6	7.0 mm
PB3	#7	7.5 mm
PB2	#8	8.0 mm
PB1	#9	N/A

To avoid confusion, you may wish to order bottom pins by size (mm) rather than #number.