Stack and reach
How high and how far forward the top of the head tube is, from the bottom bracket. They are the two numbers that decide whether a frame can be set up like yours.
BB, or bottom bracket
The axle your cranks turn on, in the middle of the frame. Every number on this site is measured from it, because it is the one point that sits in the same place on every bike.
Headset cover
The little cap on top of the head tube, under your spacers. Most makers do not publish it, so I assume 15 mm and add 6 mm to the band, which on its own is enough to hold an answer at "probably" rather than "fits".
Stem clamp, and its centre
The collar on the steerer that your stem bolts to. I need the middle of it. Where a maker gives only the height, I assume halfway up and say so on the answer.
Steerer
The tube coming up out of the fork. The cover, the spacers and the stem all sit on it, and it is the thing a mechanic cuts to length.
Bar reach
How far forward the hoods sit from the middle of the bar. Two bars on the same stem can put your hands 20 mm apart, which is why I ask.
Setback
How far your saddle sits behind the bottom bracket.
Drop
How much lower your hands sit than your saddle. On a riser bar I count the bar's rise, so the drop is that much less than it is to the clamp.
Rails, and the rail centre
The two rods under your saddle, and the middle of the straight part of them. That midpoint is the point I use, because it is the one you can find with a tape.
The band
How far out I could be, in millimetres, and why. It is a straight sum of everything I had to assume rather than a clever average, so it errs wide on purpose.
wb, stand, trail
Wheelbase, standover and trail: how long the bike is, how high the top tube is where you straddle it, and how steady the steering feels. I show them against your bike, and I leave them out when the maker does not publish them.
est.
Estimated: a number I worked out rather than read off the maker's table. Anything marked this way can move if the maker publishes the real one.
Close Escape closes it. The measuring guide has the pictures. Open the measuring guide
Mason Bokeh
Gravel · 8 sizes
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This is the bike I ride
No account is needed to read the table. Report a wrong number · Correct this bike
- Bike
- Mason Bokeh · Gravel · 8 sizes
- Versions
- Current · 2023, this table
- Geometry
- bikeinsights.com, fetched 20 Oct 2026
These numbers are second-hand, from Bike Insights. I have not checked them against the maker's own table. Bike Insights cites masoncycles.cc. - Cockpit
- Generic stem and bar, assumed
- Solved with
- cover 15 mm (assumed), max spacers 40 mm (assumed), stem clamp centre 20 mm (assumed), so every verdict carries ±10 mm at the bar
- Sheet
- 22 October 2026 · 686 bikes, 74 makes, 3,984 sizes in the catalogue
Geometry, every size, from Bike Insights
The tinted row is the size drawn beside it. Press a size to draw it.| Size | Stack (mm) | Reach (mm) | Head angle (deg) | Seat angle (deg) | Head tube (mm) | Chainstay (mm) | Wheelbase (mm) | Standover (mm) |
|---|---|---|---|---|---|---|---|---|
| 48CM | 536.1 | 359.9 | 69.5 | 74 | 100 | 435 | 1013 | 741 |
| 50CM | 537.9 | 363.5 | 70 | 74 | 115 | 435 | 1013.7 | 764.1 |
| 52CM | 554 | 374 | 70.5 | 74 | 130 | 435 | 1021.8 | 781.8 |
| 54CM | 568.1 | 376.2 | 71 | 73 | 145 | 435 | 1028.4 | 799.4 |
| 56CM | 579.5 | 383.4 | 71.5 | 73 | 155 | 435 | 1034.4 | 814.8 |
| 58CM | 587.9 | 395.2 | 72 | 72.5 | 165 | 435 | 1045.4 | 831 |
| 60CM | 607 | 399.1 | 72 | 72.5 | 185 | 435 | 1055.4 | 850 |
| 62CM | 630.7 | 401.4 | 72 | 72.5 | 210 | 435 | 1065.5 | 871.7 |
The table runs on to the right: 6 more columns after Reach. Scroll it sideways to read them.
The 56CM drawn to scale from the table, with no build on it. Stack and reach run from the bottom bracket to the top of the head tube; every size is solved from those two. One square is 100 mm.
The maker's cockpit
No stock cockpit I can name, so every size is solved on a generic stem and bar unless you choose one on the sheet.Generic stem and barAssumedNo bar is listed for this frame.
Stock stem and bar per size48CM 70 x 400, 50CM 80 x 420, 52CM 90 x 420, 54CM 100 x 440, 56CM 110 x 440, 58CM 110 x 460, 60CM 120 x 460, 62CM 120 x 460 (stem length x bar width, mm)
Frame facts
not read off the maker's page yet: masoncycles.cc- Tyre clearance
- not recorded yet
- Bottom bracket
- not recorded yet
- Axles and brakes
- not recorded yet
- UDH
- not recorded yet
- Seatpost
- not recorded yet
- Frame weight
- not recorded yet
Notes on the cockpit
Kept whole, as I read it off bikeinsights.com.No cockpit with the frameset; complete builds came with a two-piece bar and stem.
Cockpit and seatpost · 44 words
No cockpit with the frameset; complete builds came with a two-piece bar and stem. Bike Insights records the size's stock stem (70 to 120 mm) and handlebar width (40 to 46 cm, converted to mm here) from its build data; no bar is named.
SECOND-HAND NUMBERS, NOT CHECKED AGAINST THE MAKER: Bike Insights' record of the Mason Bokeh 3 (its "2023" version), eight sizes 48CM to 62CM. Source: aggregator (Bike Insights): the Bokeh "2023" version (build "3") on bikeinsights.com, numbers read from the page's __NEXT_DATA__ data script; the maker's page it cites now serves the Bokeh 3.5 chart (mason-bokeh.json), so the Bokeh 3 table is no longer published by Mason
How I read Bike Insights' table
Mason's own page for this frame (https://masoncycles.cc/products/bokeh-3-frameset, the source Bike Insights cites) now serves the Bokeh 3.5 chart, which differs on stack, reach, top tube, BB drop, head angle, wheelbase and the 58-62CM chainstay (mason-bokeh.json), so Bike Insights is the source of last resort (D4 second amendment). Trail is not stored by Bike Insights (only computed), so trail is null. Bike Insights' base build lists a 622 mm rim with a 40 mm tyre (max 55 mm); wheel_size is left null because the maker's Bokeh charts state 650b and 700c options. FLAGGED FOR CARL: the 48CM row (stack 536.1, reach 359.9, top tube 515.9, head tube 100, wheelbase 1013, standover 741) repeats the current Exposure 48CM row cell for cell (mason-exposure.json) and has a 77 mm BB drop against 75 mm on the 50CM, so it may have been copied from the Exposure; Bike Insights' 2019 and 2020 Bokeh versions have no 48CM. Those 2019 and 2020 versions match this 2023 record on every compared cell of the seven sizes they share (50CM to 62CM), so this one file stands for all three. Bike Insights cites the maker's page: https://masoncycles.cc/products/bokeh-3-frameset.