Searches for 650x52B, 27.5x2.10 and ETRTO 52-584 are usually about the same wheel family: a 584 mm rim with a tyre around 52 mm wide. The confusion comes from old French 650B naming, modern 27.5 inch mountain-bike naming and ETRTO all appearing on similar products.
Why 52-584 is the key marking
The second ETRTO number, 584, is the rim diameter. A 52-584 tyre will not fit a 559 mm 26 inch rim or a 622 mm 700C rim. The first number is the approximate width. Nearby tyres such as 50-584 and 54-584 may be useful alternatives, but they are still different widths and need a clearance check.
650B gravel versus 27.5 MTB wording
A 650B gravel tyre often uses road/gravel language and may have a faster tread, while a 27.5 MTB tyre may use mountain-bike tread and casing language. Both can use the 584 mm rim diameter. Choose based on surface and bike clearance, not only the name: fast road/gravel, mixed paths, loose trails and muddy MTB routes need different tread patterns.
Catalogue examples and nearby sizes
1Bike currently has nearby 584 mm options such as the Schwalbe G-One Speed 27.5x2.00 / 650x50B / 50-584 for fast gravel-style use and the Schwalbe Racing Ralph 27.5x2.10 / 54-584 as a more MTB-oriented comparison point. Treat these as related sizes, not automatic substitutes for an exact 52-584 unless your bike has the clearance and the use case matches.
Matching inner tubes
A tube can cover a range of tyre widths. For this wheel family, check tubes such as Mitas 27.5x1.50/2.10 Presta 37/54-584/597, Hutchinson Protect'Air 47/57-584 Schrader or Schwalbe AV19 40/62-584/635 Schrader. The printed range must include your tyre width, and the valve must fit the rim hole.
Common mistakes
Do not buy a tyre just because it says 650 or 27.5. Check the exact ETRTO. Do not assume 50-584, 52-584 and 54-584 all clear the same frame. Do not fit a very aggressive MTB tread on a close-clearance gravel frame without checking mud room. If the old sidewall is worn, photograph the tyre, rim and available clearance before choosing.
