Every reference with a known width takes the same strap size. Your reference is engraved on the case back or between the lugs at 6 o'clock.
21 mm
Verification: Two sources agree on ref. 310.92.44.50.01.001 and 311.92.44.51.01.007
44.2 mm case
Indicative information. Check your watch before buying a strap: whatsmylugwidth.com is not responsible for an incorrect size.
The Omega Speedmaster Dark Side takes a 21 mm strap: all 8 references with a listed width in our database use 21 mm. Check the reference on your case back to be sure.
Omega Speedmaster Dark Side references in our database. Each card says where its width comes from: listed by the maker (linked to the maker's page in the details), two independent sources agree, or listed in our database and not yet verified by us.
Speedmaster Dark Side Apollo 8 Speedmaster Dark Side Of The Moon Chronograph 44.25mm - Black on Rubber Strap
Lug width: 21 mm
Source: Two sourcesCase size: 44.2 mmBlack dialCase material: Black Ceramic
Speedmaster Dark Side of the Moon Black Ceramic 44.25mm - Black on Fabric Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmBlack dialCase material: Black ceramic
Speedmaster Dark Side of the Moon Black Ceramic 44.25mm - Black on Rubber Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmBlack dialCase material: Black ceramic
Speedmaster Dark Side of the Moon Black Ceramic 44.25mm - Full Black on Fabric Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmBlack dialCase material: Black ceramic
Speedmaster Dark Side of the Moon Black Ceramic 44.25mm - Full Black on Rubber Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmBlack dialCase material: Black ceramic
Speedmaster Dark Side of the Moon Black Ceramic 44.25mm - Full Black w/ Red Seconds Hand on Rubber Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmBlack dialCase material: Black ceramic
Speedmaster Dark Side Of The Moon Chronograph 44.25mm - Black on Fabric Strap
Lug width: 21 mm
Source: Two sourcesCase size: 44.2 mmBlack dialCase material: Black Ceramic
Speedmaster Dark Side Of The Moon Chronograph 44.25mm - Grey on Leather Strap
Lug width: 21 mm
Source: DatabaseCase size: 44.2 mmGrey dialCase material: Grey Ceramic
No reference matches.
The Omega Speedmaster Dark Side takes a 21 mm strap: all 8 references with a listed width in our database use 21 mm. Check the reference on your case back to be sure. The Omega Speedmaster Dark Side ref. 310.92.44.50.01.001 and 311.92.44.51.01.007 take 21 mm (two independent sources agree).
From our database, which lists 8 Omega Speedmaster Dark Side references, 8 of them with a listed width. Each reference card says whether the maker lists the width, two independent sources agree on it, or it is not yet verified.
The gap between the two lugs that hold the strap, in millimetres. A new strap must match it exactly: 20 mm lugs take a 20 mm strap.
Most watches use spring bars, so any strap of the right width fits. Many smartwatches use their own band system instead, such as Apple Watch bands or Garmin QuickFit.