Fowler High Precision The Fowler/Bowers XT measuring heads are only compatible with Fowler/Bowers XT bore gages. The XT heads are compatible with the following Fowler/Bowers bore gages: XTA Mechanical Holemikes XT, XTD, and XT3 Electronic Holemikes XT, XTH, and XT3 Holematic Pistol Grip Bore Gages Individual Fowler/Bowers XT Spherical Anvils Holematic Heads: 54-343-006: Fowler/Bowers XT Measuring Head with Spherical Anvils: .080-.100"/2-2.5mm 54-343-007: Fowler/Bowers XT Measuring Head with Spherical Anvils: .100-.120"/2.5-3mm 54-343-008: Fowler/Bowers XT Measuring Head with Spherical Anvils: .120-.160"/3-4mm 54-343-009: Fowler/Bowers XT Measuring Head with Spherical Anvils: .160-.200"/4-5mm 54-343-010: Fowler/Bowers XT Measuring Head with Spherical Anvils: .200-.250"/5-6mm 54-343-011: Fowler/Bowers XT Measuring Head with Spherical Anvils: .250-.312"/6-8mm 54-343-012: Fowler/Bowers XT Measuring Head with Spherical Anvils: .312-.375"/8-10mm 54-343-013: Fowler/Bowers XT Measuring Head with Spherical Anvils: .375-.500"/10-12.5mm 54-343-014: Fowler/Bowers XT Measuring Head with Spherical Anvils: .500-.625"/12.5-16mm 54-343-015: Fowler/Bowers XT Measuring Head with Spherical Anvils: .625-.750"/16-20mm 54-343-016: Fowler/Bowers XT Measuring Head with Spherical Anvils: .750-1"/20-25mm 54-343-017: Fowler/Bowers XT Measuring Head with Spherical Anvils: 1-1.375"/25-35mm 54-343-018: Fowler/Bowers XT Measuring Head with Spherical Anvils: 1.375-2"/35-50mm 54-343-019: Fowler/Bowers XT Measuring Head with Spherical Anvils: 2-2.625"/50-65mm 54-343-020: Fowler/Bowers XT Measuring Head with Spherical Anvils: 2.625-3.250"/65-80mm 54-343-021: Fowler/Bowers XT Measuring Head with Spherical Anvils: 3.250-4"/80-100mm 54-343-022: Fowler/Bowers XT Measuring Head with Spherical Anvils: 4-5"/100-125mm 54-343-023: Fowler/Bowers XT Measuring Head with Spherical Anvils: 5-6"/125-150mm 54-343-024: Fowler/Bowers XT Measuring Head with Spherical Anvils: 6-7"/150-175mm 54-343-025: Fowler/Bowers XT Measuring Head with Spherical Anvils: 7-8"/175-200mm 54-343-026: Fowler/Bowers XT Measuring Head with Spherical Anvils: 8-9"/200-225mm 54-343-027: Fowler/Bowers XT Measuring Head with Spherical Anvils: 9-10"/225-250mm 54-343-028: Fowler/Bowers XT Measuring Head with Spherical Anvils: 10-11"/250-275mm 54-343-029: Fowler/Bowers XT Measuring Head with Spherical Anvils: 11-12"/275-300mm