The Series 516 112-piece 1 mm base metric rectangular gage block set ships 9 individual blocks sized 1.001 mm through 1.009 mm in 0.001 mm increments, forming the finest-resolution subgroup in the standard configuration [S1][S4].
A complete 112-piece set breaks down as: 1 block at 1.0005 mm, 9 blocks at 1.001-1.009 mm (0.001 mm step), 49 blocks at 1.01-1.49 mm (0.01 mm step), 19 blocks at 0.5-9.5 mm (0.5 mm step), and 10 blocks at 10-100 mm (10 mm step) [S1]. The 1.001-1.009 mm subgroup exists specifically to resolve the sub-2 mm length domain that drives micrometer/caliper calibration below the 1.0 mm lower limit of a standard micrometer anvil.
Set Composition and Block Count Math
The 9 blocks in the 1.001-1.009 mm series plus the 1.0005 mm block total 10 sub-2 mm fractional blocks, matched by another 9 blocks in 0.01 mm steps covering 1.01-1.09 mm, which together with the 0.5 mm step blocks and 10/25 mm step blocks reach the canonical 112 count [S1][S6].
Mitutoyo publishes 4 steel grade options (K, 00, 0, 1) and 4 CERA ceramic grade options, with order numbers 516-531-56 (K), 516-937-26 (00), 516-938-26 (0), and 516-939-26 (1) for the 112-piece steel set, and 516-541-56 / 516-337-26 / 516-338-26 / 516-339-26 for the parallel CERA lineup [S1]. The 1.001-1.009 mm block count and identity are identical across all grades; only the dimensional tolerance and price tier change.
Steel vs CERA Ceramic: Material Trade-off
Steel blocks in this series are high-carbon, high-chrome steel receiving a specific repeated heat treatment that reduces dimensional change over service life; CERA ceramic blocks are advertised as "free from dimensional change over time" with approximately 10x the abrasion resistance of equivalent steel blocks [S3].
Both materials share the same nominal 1.001-1.009 mm step pattern and ship in a solid wooden case with an Inspection Certificate; ISO/IEC 17025 certification is available as an option on the steel set [S3]. For shop-floor metrology rooms without climate control, the CERA version's corrosion resistance and thermal stability (typical ceramic TC near 6-8 x 10^-6/K vs steel near 11.5 x 10^-6/K) is the more conservative choice, while the steel set remains the price baseline.
Grade Selection and Tolerance Bands
Grade 00 (order number 516-937-26 for steel) is the highest-accuracy grade Mitutoyo lists for the 112-piece 1 mm base set, targeting primary calibration laboratory use; Grade 0 (516-938-26) is the workhorse inspection-room grade priced at $4,740 per set at TestEquity listing [S3][S4].
Lower grades K (516-531-56) and 1 (516-939-26) extend the lineup into workshop-grade applications where absolute tolerance bands of micrometer calibration at the 1-10 mm range are less critical; the 1.001-1.009 mm block itself is the same physical part, only the inspection certificate grade and acceptance limits differ [S1]. Buyers specifying ASME B89.1.5 / ISO 3650 traceability should match grade to use case rather than over-specifying the ceramic premium.
Comparison: 1 mm Base Rectangular vs 2 mm Base Square Sets
Starrett-Webber's 1 mm base rectangular layout carries 9 blocks of 1.001-1.009 mm at 0.001 mm step, whereas a 2 mm base square set substitutes 2.001-2.009 mm at the same 0.001 mm step; the rectangular form factor is therefore mandatory when a calibration point between 1.000 and 2.000 mm is needed [S2].
On three decision criteria: (a) coverage below 2 mm, the 1 mm base set wins because it includes both 1.0005 mm and the 1.001-1.009 mm series; (b) face area and wringability, the square 2 mm base set offers larger contact area for longer stacks; (c) cost-to-accuracy ratio, the 112-piece rectangular set covers more discrete length points per dollar because 28 of its 45 unique sizes sit in the sub-10 mm fractional domain [S2]. This is why most metrology labs standardise on the 1 mm base rectangular form for caliper and micrometer calibration, and reserve 2 mm base square sets for height-master and long-block applications.
Calibration Application Domain
The 1.001-1.009 mm block series is the smallest-resolution subgroup in the set and is normally wrung together with the 1.0005 mm block and 1.01-1.49 mm blocks to build discrete length points from 1.0005 mm upward in 0.001 mm or 0.01 mm increments for micrometer zero-setting and caliper jaw-gap verification [S1][S2].
For instrument builders who routinely calibrate sub-2 mm inside-measuring tools (small bore gages, point micrometers, thread-measuring wire sets), the 1 mm base rectangular 112-piece set is the de-facto reference, with the 1.001-1.009 mm series acting as the resolution backbone [S2]. Material choice within that set then splits between high-carbon/chrome steel for general use and CERA ceramic for thermal-stability-critical or corrosive-environment labs.
Sourcing, Standards, and Order Codes
Order number 516-938-26 (steel Grade 0) is the most commonly listed SKU for the 112-piece set with the 1.001-1.009 mm subgroup, currently shown at $4,740 per set at TestEquity, while 516-937-26 covers Grade 00 and 516-531-56 covers Grade K [S3][S4][S1]. The CERA equivalents use the 516-3xx-26 and 516-541-56 numbering block, with identical block composition [S1].
Traceability is documented via the included Inspection Certificate, with optional ISO/IEC 17025 accredited certification available on the steel set [S3]. Standards governing the geometry and tolerance of these blocks are ISO 3650 (length standards) and ASME B89.1.5, both of which define grade-by-grade flatness, parallelism, and length-deviation envelopes that the 1.001-1.009 mm series must meet. For more on how precision length standards interface with downstream instrumentation, see our gage block selection guide, and for material-grade selection context on adjacent tooling, the 1.1730 vs 1.2311 vs 1.2312 mold base steel comparison covers parallel material trade-off logic.
Spec-level background on the components involved: pressure transmitter, flow meter, and industrial valve.