Prospex 1968 Heritage Diver's GMT
Ref. SPB381
- Case diameter
- 42 mm
- Manufacturer spec
- Lug-to-lug
- 48.6 mm
- Manufacturer spec
- Thickness
- 12.9 mm
- Manufacturer spec
- Lug width
- 20 mm
- Manufacturer spec
Retail price $1,500 (US, Oct 2026)
How the Prospex 1968 Heritage Diver's GMT wears
Its lugs add 6.6 mm to the 42 mm case, close to the 7 mm typical across the almanac, so its diameter is a fair guide to how it wears.
On our fit model it sits best on wrists from 6.75" to 8" (17.1–20.3 cm); below 6.75" the lugs start to reach the edge of the wrist.
At 12.9 mm thick it is slimmer than 52% of the 124 other dive watches we've measured, so it slides under a cuff more easily than most.
Its 20 mm lug width is one of the most common strap sizes; 156 other watches here share it, so aftermarket straps are easy to find.
Will the Prospex 1968 Heritage Diver's GMT fit your wrist?
With a 48.6 mm lug-to-lug, here is how it wears across common wrist sizes. We estimate the flat top of each wrist from its circumference; measure yours for a closer answer in the fit finder.
| Wrist | Flat width (est.) | Fit |
|---|---|---|
| 6" | 47.2 mm | Lugs overhang |
| 6.5" | 51.2 mm | Snug, lugs near the edge |
| 7" | 55.1 mm | Ideal fit |
| 7.5" | 59.1 mm | Ideal fit |
| 8" | 63 mm | Ideal fit |
Specifications
- Reference
- SPB381
- Collection
- Prospex
- Status
- In production
- Case material
- stainless steel (ceramic bezel display)
- Crystal
- sapphire (inner AR coating)
- Water resistance
- 200 m
- Bezel
- unidirectional diver's bezel
- Dial
- green
- Strap / bracelet
- stainless steel bracelet, three-fold clasp with secure lock, push button release and extender
- Weight
- 176 g
- Style
- Dive, GMT
Movement
- Caliber
- Seiko 6R54
- Type
- automatic
- Power reserve
- 72 hours
- Jewels
- 24
- Accuracy
- +25/-15 s/day
Takes 20 mm straps. See other 20 mm watches and straps.
More Prospex references
- SeikoProspex 1965 Diver's Modern Re-interpretationSPB143 · “62MAS reinterpretation”
- Case
- 40.5 mm
- Lug-to-lug
- 47.6 mm
- Thick
- 13.2 mm
- SeikoProspex 1965 Heritage Diver'sSPB451
- Case
- 40 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 13 mm
- SeikoProspex 1970 Diver's Modern Re-interpretationSPB317 · “Captain Willard”
- Case
- 41 mm
- Lug-to-lug
- 46.9 mm
- Thick
- 12.3 mm
- SeikoProspex AlpinistSPB121 · “Alpinist”
- Case
- 39.5 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 13.2 mm
- SeikoProspex AlpinistSPB507
- Case
- 39.5 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 12.7 mm
- SeikoProspex AlpinistSPB503
- Case
- 39.5 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 12.7 mm
- SeikoProspex AlpinistSPB209
- Case
- 39.5 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 13.2 mm
- SeikoProspex AlpinistSPB505
- Case
- 39.5 mm
- Lug-to-lug
- 46.4 mm
- Thick
- 12.7 mm
- SeikoProspex Diver SamuraiSRPB49 · “Samurai”
- Case
- 43.8 mm
- Lug-to-lug
- 48 mm
- Thick
- 13 mm
- SeikoProspex Diver's 200mSPB101 · “Sumo”
- Case
- 45 mm
- Lug-to-lug
- 52.6 mm
- Thick
- 12.9 mm
- SeikoProspex Diver's 200mSPB103 · “Sumo”
- Case
- 45 mm
- Lug-to-lug
- 52.6 mm
- Thick
- 12.9 mm
- SeikoProspex Diver's 200m TitaniumSPB189 · “Shogun”
- Case
- 43.5 mm
- Lug-to-lug
- 51 mm
- Thick
- 13.3 mm
- SeikoProspex Land Mechanical 38mmSPB249
- Case
- 38 mm
- Lug-to-lug
- 46.2 mm
- Thick
- 12.9 mm
- SeikoProspex Marinemaster 1965 Heritage Diver'sSJE117
- Case
- 39.5 mm
- Lug-to-lug
- 47.2 mm
- Thick
- 12.3 mm
- SeikoProspex Marinemaster 1968 Heritage Diver's 300mSLA077
- Case
- 42.6 mm
- Lug-to-lug
- 49.3 mm
- Thick
- 13.4 mm
- SeikoProspex Monster PADI Special EditionSRPE27 · “Monster”
- Case
- 42.4 mm
- Lug-to-lug
- 49.4 mm
- Thick
- 13.4 mm
- SeikoProspex Sea TurtleSRPE93 · “Turtle”
- Case
- 45 mm
- Lug-to-lug
- 47.7 mm
- Thick
- 13.4 mm
- SeikoProspex Solar Hybrid Diver's 1982 Modern Re-interpretationSNJ025 · “Arnie”
- Case
- 47.8 mm
- Lug-to-lug
- 50.5 mm
- Thick
- 13.8 mm
- SeikoProspex Speedtimer MechanicalSPB513
- Case
- 39.5 mm
- Lug-to-lug
- 44.5 mm
- Thick
- 12 mm
- SeikoProspex Speedtimer Mechanical ChronographSRQ047
- Case
- 42 mm
- Lug-to-lug
- 49.5 mm
- Thick
- 14.6 mm
- SeikoProspex Speedtimer Solar ChronographSSC911
- Case
- 41.4 mm
- Lug-to-lug
- 45.9 mm
- Thick
- 13 mm
- SeikoProspex Speedtimer Solar Chronograph 39mmSSC961
- Case
- 39 mm
- Lug-to-lug
- 45.5 mm
- Thick
- 13.3 mm
Watches that wear the same size
Other watches within 1.5 mm of its lug-to-lug.
- OmegaSpeedmaster Chronoscope 43329.30.43.51.02.001
- Case
- 43 mm
- Lug-to-lug
- 48.6 mm
- Thick
- —
- OmegaSpeedmaster Moonphase Meteorite304.30.43.52.01.001
- Case
- 43 mm
- Lug-to-lug
- 48.6 mm
- Thick
- 13.6 mm
- CasioCasio Duro MDV-106MDV-106-1AV · “Duro”
- Case
- 44.2 mm
- Lug-to-lug
- 48.5 mm
- Thick
- 12.1 mm
- CasioG-Shock GA-2100GA-2100-1A1 · “CasiOak”
- Case
- 45.4 mm
- Lug-to-lug
- 48.5 mm
- Thick
- 11.8 mm
- CasioG-Shock GA-B2100GA-B2100-1A
- Case
- 45.4 mm
- Lug-to-lug
- 48.5 mm
- Thick
- 11.9 mm
- Grand SeikoElegance Spring DriveSBGA407 · “Skyflake”
- Case
- 40.2 mm
- Lug-to-lug
- 48.5 mm
- Thick
- 12.8 mm
Same 20 mm lug width
All 20 mm watchesThese take the same straps as the Prospex 1968 Heritage Diver's GMT.
- AutodromoMonoposto Series Two (Moss Green)BP-002-MG
- Case
- 43 mm
- Lug-to-lug
- 46 mm
- Thick
- 11 mm
- BalticAquascaphe Classic
- Case
- 39 mm
- Lug-to-lug
- 47 mm
- Thick
- 13 mm
- BalticAquascaphe Dual-Crown Black
- Case
- 39 mm
- Lug-to-lug
- 47 mm
- Thick
- 11.9 mm
- BalticAquascaphe GMT MK II
- Case
- 39.5 mm
- Lug-to-lug
- 47 mm
- Thick
- 13.8 mm
- BalticAquascaphe MK2 37mm
- Case
- 37 mm
- Lug-to-lug
- 45 mm
- Thick
- 12.9 mm
- BalticAquascaphe MK2 39.5mm
- Case
- 39.5 mm
- Lug-to-lug
- 47 mm
- Thick
- 12.9 mm