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 Most makers do not publish it, so I assume 15 mm and add 6 mm to the band, which on its own is enough to hold an answer at "probably" rather than "fits".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 InSearchOf
Gravel · 5 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 InSearchOf · Gravel · 5 sizes
- Geometry
- masoncycles.cc, fetched 20 Oct 2026, re-checked, no differences
- 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 the maker's table
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)not published |
|---|---|---|---|---|---|---|---|---|
| 42CM | 606 | 366.6 | 69 | 74 | 100 | 445 | 1062.1 | |
| 46CM | 614.4 | 375.7 | 69 | 74 | 110 | 445 | 1075 | |
| 50CM | 623.8 | 379.4 | 69 | 74 | 120 | 445 | 1082.3 | |
| 54CM | 633.1 | 384 | 69 | 74 | 130 | 445 | 1090.2 | |
| 58CM | 654.5 | 397.4 | 70 | 74 | 150 | 445 | 1101.3 |
The table runs on to the right: 6 more columns after Reach. Scroll it sideways to read them.
The 50CM 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 size42CM 70 x 420, 46CM 70 x 440, 50CM 80 x 460, 54CM 90 x 460, 58CM 100 x 480 (stem length x bar width, mm)
Frame facts
read from the maker's words, not a table: masoncycles.cc- Tyre clearance
- 29 x 2.6 in, 650b x 2.9 in
- Bottom bracket
- not recorded yet
- Axles and brakes
- not recorded yet
- UDH
- not recorded yet
- Seatpost
- not recorded yet
- Frame weight
- not recorded yet
In the maker's words
Kept whole, as I read it off masoncycles.cc.No cockpit with the frameset; complete builds come with bars, stem and cranks "pre-set to match frame size".
Cockpit and seatpost, in the maker's words · 77 words
No cockpit with the frameset; complete builds come with bars, stem and cranks "pre-set to match frame size". The chart's STEM row prints stem lengths 70, 70, 80, 90, 100 (42CM to 58CM) mm and its HANDLEBAR (OUTSIDE DIMENSION) row prints 420, 440, 460, 460, 480 for 42CM to 58CM (mm, outside dimension). Two-piece bar and stem; the frameset comes with a Deda headset, expander bung and top cap; no bar is named on the frameset page.
OFFICIAL SOURCE: Mason Cycles product page for the ISO 2 Frameset (URL insearchof-frameset. Source: html table (official Mason Cycles product page "ISO 2 Frameset", the "Full geometry chart" table in the page markup; fetched 2026-10-20
How I read the maker's table
"The updated ISO2 is a progressive frame and fork with a design allowing use of 29 x 2.6” or 650b x 2.8" wheels"), five sizes 42CM to 58CM, labels as printed. Some angle cells carry a degree sign in the markup (71.5º), stripped by the parser. Stack datum: the page's geometry diagram (/media/images/diagram-geometry.png, read for the datum only, not stored) draws stack and reach to the head tube top; no headset cover height is given. This chart has no single STAND-OVER row: it prints "S/O - 27.5 x 2.8 (Measured vertically, 50mm in front of BB centre)" 74.0/76.5/79.0/82.5/86.5 and "S/O - 29 x 2.4 (...)" 76.0/78.5/81.0/84.5/88.5, with no unit (they read as centimetres), so standover is null and both rows are kept here. The headline TRAIL row equals the TRAIL: 29 x 2.4" row (89.6 x4, 82.6), so the trail is for 29 x 2.4 in tyres (wheel_size 700c is the 29 in / 622 rim; tyre_width_mm null). stock_bar_width is the HANDLEBAR (OUTSIDE DIMENSION) row as printed (mm); it is the bar's OUTSIDE dimension as the maker labels it, not centre to centre. FORK CROWN HEIGHT 483 (100 mm suspension-corrected, HotShoe2 fork); AXLE SPACING 148; frame weights 2100g to 2480g; RIDER HEIGHT GUIDE cm 151-163 to 188-198. Clearance: "29" or 27.5" wheels - max tyre width: 29 x 2.6” or 27.5 x 2.9”". Model year: not printed on the page (model_year null). Bike Insights files this frame as "ISO 2" (2025) and the earlier frame as "InSearchOf" (2022, 2021, 2019).
Source: html table (official Mason Cycles product page "ISO 2 Frameset", the "Full geometry chart" table in the page markup; fetched 2026-10-20, HTTP 200)