While it's true that "i" is usually the slice where FAT/MSDOS partitions fall, you can find out for sure by doing something like this:
Code:
# disklabel sd0
# /dev/rsd0c:
type: SCSI
disk: SCSI disk
label: U3 Cruzer Micro
duid: be87cc821c90eada
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 255
sectors/cylinder: 16065
cylinders: 498
total sectors: 8015505
boundstart: 0
boundend: 8015505
drivedata: 0
16 partitions:
# size offset fstype [fsize bsize cpg]
c: 8015505 0 unused
i: 8000306 64 MSDOS
#