Bouts = "leftover" randomly-shaped trapezoids/rhomboids/etc. that remain after first extracting as many rectangles as possible.  For the record, they obviously had bouts available to them miners to try and sell a century and a half ago, too...I guess back then they assumed there'd be plenty of rocks forever.

Bouts are great for establishing bevels, and present no limitations at all for water-only finishing to me.   Depending upon their shape, they can be limiting for going from bevel-making to the final finish via continually watered down slurry, and thus you can see the rationale behind why my primary preference is for stones with ultra-high water-only speed.   With enough square footage (particularly in any one long axis), bouts are absolutely fine and of no meaningful difference.   Bouts are always the best value per unit of area, too.

Bouts are cool; I'm privileged enough to say I was once briefly an Aspen, Colorado ski bum (94-95, ask me about mid-Feb. when we had ~100" in 10 days followed up by 26" after the lifts closed and before they opened, people were hurling themselves off the Steeplechase edge just to land in bottomless chicken feathers), and bouts remind me of skiing Aspen Highlands instead of Aspen Mountain.   While the latter's more famous, nearly every run falls straight to earth...most runs on "Highlands", however, simultaneously fall down and to a side.  In this opinion, one learns more of skiing in that complex realm, and one will better learn honing's essence on a bout than on a rectangle.  Honing's primarily about what you're feeling with any one part of the edge at any one time on any one part of the stone.   Become accomplished living that philosophy and you can hone upon circles.  To loosely quote the brilliant 1980 masterpiece Caddyshack, "be the edge" :-)

• # 3 Bouts = 22-27 sq. cm a perfectly-average "perfect" parallelogram would be 1.9 x 1.9" (49x49mm)
• # 4 Bouts = 27-33 sq. cm a perfectly-average "perfect" parallelogram would be 2.16 x 2.16" (55x55mm)
• # 5 Bouts = 33-39 sq. cm, a perfectly-average "perfect" parallelogram would be 2.4 x 2.4" (60x60mm)
• # 6 Bouts = 39-48 sq. cm, a perfectly-average "perfect" parallelogram would be 2.6 x 2.6" (66x66mm)
• # 7 Bouts = 48-58 sq. cm a perfectly-average "perfect" parallelogram would be 2.9 x 2.9" (73x73mm)
• # 8 Bouts = 58-70 sq. cm a perfectly-average "perfect" parallelogram would be 3.15 x 3.15" (80x80mm)
• # 9 Bouts = 70-84 sq. cm, a perfectly-average "perfect" parallelogram would be 3.45 x 3.45" (88x88mm)
• # 10 Bouts = 84-102 sq. cm, a perfectly-average "perfect" parallelogram would be 3.8 x 3.8" (97x97mm)

What lies below is amongst what we're best known for as a shaving shop.

The most challenging bout (polygon) shape to me is an isoceles triangle, and the easiest a parallelogram.  With plain water use for touch-up/finishing work, to me any shape's of no limitation.

EVERY NON-SLURRY-SIZE BELGIAN COTICULE STONE WE SELL IS "LAPPED" FLAT TWICE, ONCE IN BELGIUM (on a spinning wheel) & AGAIN @ OUR SHOP (on the DMT Dia-Flat© Lapping Plate).  You don't have to pay extra for it because its cost in time is already included in the stones' selling prices.

If you'd like to have a stone with the geometric advantages used by all Solingen master grinders, however, we can supply!  [full disclosure; in Germany they prepare these entirely by hand and it takes on a dual-axis convexing, what's offered here is strictly a sphere]   This service option gives you a convex stone, not a flat one...use your slurry stone upon it in circles moving away from the 'summit' of your hone to generate wear away from the middle that we tend to use the most, and it should be able to maintain the convex shape perpetually.  The convexing is subtle but nonetheless perfectly represented and quite uniform in a spherical gradient.

Why do they (all) do this where they're made?  Because 1) it reduces spine wear, 2) it solves all problems with warped razors or razors of varying thickness, 3) it isolates the contact patch to a narrow point to provide better feedback, 4) it guarantees that with each stroke the entirety of the spine and edge will receive contact, as opposed to a variably-thick razor being used on a 'normal' flat stone which will merely grind away the thickest parts of the razor until all is of one width, and 5) it makes the bevel plane angle marginally more acute than is possible with a flat stone (actually the master grinders by and large prefer to use flat wheels/belts until the bench stone, and the bench stone is only to alter the acuity of the very last bit of the bevel plane width rather than cut in an entire bevel plane with the increased acuity).  Give it a good think and consider the worth of this for yourself, don't let others online or here do your thinking, but remember that the use of the convex hone is univeral and the proof of proper preparation of such a benchmark test during one's apprenticeship.

Technically, one can confidently use the entirety of such a stone just as with a flat stone, because the relationship between blade and stone alignment is not changing (you're essentially working the razor upon the outside of an enormous sphere-shaped hone).   However, it is typical among master grinders that a honer reach the 'summit' and then take the razor off the stone and return to an outer boundary to come back to 'summit' once again from the other side of the blade.  This seems more habit than strict rule, possibly because it may develop good muscle memory buildup quickly but also because while the stone/razor geography's always the same, the relationship of the weight of the razor spine and edge relative to the gravity below the stone will alter "downhill" vs "uphill", and if an edge is always "uphill" the quantity of pressure applied by the honer might remain more uniform than if it is changing from "uphill" to "downhill" with each stroke.

The spherically convex stone can be used for any size, but in this opinion presents its largest advantage with larger stones.

Convex My Coticule
$10 In-Stock (duh)