Mustad 3551 Treble Hook: Size Chart and OEM Equivalent Spec Guide

Searches for the Mustad 3551 come from two kinds of buyer. One is a lure builder matching a hook to a mould he already owns. The other is a retail buyer checking dimensions before committing to a bulk order. Both need the same thing, which is the size chart in millimetres rather than a product photo.

This guide collects the published numbers in one table, shows where the 3551 sits relative to Mustad's heavier treble references, and lists the specification fields a factory needs before it can quote a matching treble.

What the 3551 Pattern Is

Mustad describes the 3551 as a classic round-bend treble built on Nor-Tempered wire, with a looped eye and a cut point. It is catalogued for plugs, spoons, pilkers, and spinners.

Round bend with a standard shank is a specific geometry. The bend forms a wide circle, so the gape is large and the point stands away from the shank. On a hard bait that geometry engages earlier when a fish slaps the lure.

The 3551 is the standard-wire reference in this family. Mustad sells the heavier versions under separate numbers: 3565 and 3567B are listed as 2X strong, and 3599C as 4X strong. A spec sheet that names 3551 is asking for the standard-wire hook.

Published Dimensions by Size

The table below reproduces Mustad's published size chart for the 3551 bronze reference. Wire diameter, gap, and overall length are given per size in millimetres.

Hook size	Wire diameter (mm)	Gap (mm)	Length (mm)
6	0.84	6.8	20
4	0.93	8.0	24
2	1.02	9.5	28
1	1.07	10.3	30
1/0	1.15	11.5	33
2/0	1.25	12.7	36
3/0	1.42	14.0	39
4/0	1.62	15.0	43
5/0	1.72	16.3	47
6/0	1.82	17.5	52
7/0	2.04	19.0	57
8/0	2.18	20.5	62
9/0	2.33	22.5	68
10/0	2.64	25.5	75
12/0	3.25	32.0	93
14/0	4.05	38.5	116
16/0	4.88	47.0	143
20/0	7.00	68.0	216

Mustad also lists sizes 20, 18, 16, 14, 12, 10, and 8 for this pattern, but the published page leaves the millimetre columns blank for those sizes. Treat them as catalogue entries until you have measured hardware in hand.

Reading the Table Before You Buy

Wire diameter drives two properties at once. It sets how much load the hook takes before it opens, and it sets how much force the point needs to penetrate. From size 4 to size 2/0 the diameter climbs from 0.93 mm to 1.25 mm.

Gap is the dimension that decides whether a hook fits the fish. On the 3551 the gap runs from 6.8 mm at size 6 to 15 mm at size 4/0. For a lure builder, gap is also the dimension that decides whether the treble clears the lure body on the swing.

Length is the variable with the most effect on the lure itself, because it sets where the hook sits relative to the belly. The published figures put size 4/0 at 43 mm overall and size 8/0 at 62 mm.

Where the 3551 Sits Against the 2X and 4X References

Mustad's classic treble range is split by wire strength rather than by bend. The 3551 carries the standard wire. The 3565 and 3567B are catalogued as 2X strong, and the 3599C as 4X strong. Bend geometry and shank style are largely common across the group.

At the same nominal size, a 2X reference uses a heavier wire diameter than the 3551. Two hooks that look identical in a photo can therefore behave differently under load.

The consequence for procurement is direct. If a specification references the 3551, a supplier who quotes against the 3565 has not quoted an equivalent, even at the same size.

Matching the Pattern in Our Range

Axis Hook builds treble hooks in Round Bend and O'Shaughnessy patterns from #12 to 4/0. For a standard-shank round-bend treble in the 3551 style, the corresponding models are 1213 with a Flat Point and 1215 with an SR Point.

Requirement	Mustad 3551 (published)	Axis Hook 1213 / 1215
Bend and shank	Round bend, standard shank, looped eye	Round bend, standard shank (1213, 1215)
Point	Cut point	Flat Point (1213) or SR Point (1215)
Wire diameter per size	Published per size, 0.84 mm to 7.00 mm	Not published per size. Locked on the spec sheet for each order
Size coverage	20 through 20/0	#12 through 4/0 across the treble range
Default finish	Bronze, with nickel, duratin and gold references	Black Nickel, 300 h ASTM B117. Other coatings on request
Typical use	Plugs, spoons, pilkers, spinners	Hard baits, crankbaits, pike lures, saltwater lures
Order minimum	Retail packs from 5 pieces	500 pcs per pattern. Modified wire gauge 2,000 pcs

Two rows in that table are not settled by a catalogue. Our published range does not list per-size wire diameters, so the diameter is confirmed on the spec sheet for each order. Sizes above 6/0 fall outside our current treble tooling, and a buyer who needs 8/0 and larger should treat that as a separate sourcing conversation rather than a sizing question.

What the Published Spec Sheet Does Not Cover

The public chart answers a sizing question. It leaves five fields open, and those five fields are where an OEM order is usually won or lost.

Tensile strength per size. The chart gives dimensions, not load figures.
Wire grade and temper. Nor-Tempered names a process, not a steel grade a factory can buy against.
Coating thickness, and salt-spray hours per finish.
Dimensional tolerances. A nominal millimetre figure does not state an acceptable range.
Point geometry in degrees. Cut point is a family of grinds rather than one angle.

A sample can match every published figure and still miss on tensile, on coating life, or on point angle.

Writing the Equivalent Spec for a Quote

A quote request that names a pattern and a size will come back with a price for something. These fields make it a price for the hook you actually want.

Pattern reference and bend style: round bend, standard shank, looped eye
Trade size listed individually, because the minimum order is counted per size
Wire diameter in millimetres, with a tolerance band
Gap and overall length in millimetres, with tolerances
Point type, and whether an offset is acceptable
Finish, with a salt-spray target in hours
Packaging format, and count per pack
Quantity per size, and required lead time

Wire diameter and point type change the fishing behaviour more than any other field, so both should be locked before the first sample rather than after it.

Packs, Sizes, and Order Quantities

At retail the 3551 is sold in small packs and in bulk counts, and Mustad's published reference list carries pack codes for 5, 25, 336, and 1000 pieces depending on size and finish.

OEM buying works differently. The minimum is counted per pattern and per size, so an order spread across six sizes carries six minimums rather than one. At Axis Hook the standard minimum is 500 pieces per pattern. A modified wire gauge carries a higher minimum of 2,000 pieces and adds roughly three weeks to lead time.

Consolidating a first production run to two or three sizes keeps the number of separate minimums down, and the remaining sizes can be added on the repeat order.

Verifying Samples on Arrival

Incoming inspection for trebles is short and mechanical. Measure wire diameter at the shank on ten pieces from the lot with a micrometer, then compare the spread against the tolerance band in the spec. Measure gap and overall length on the same ten pieces.

Point quality is a visual check under magnification. The grind should be symmetric, with no rolled tip, and the eye should be a closed loop with no burr.

For coated hooks, run a salt-spray sample to the hours written in the spec. Those four checks cover the properties that a dimensional table cannot confirm.

If a product line is benchmarked against the Mustad 3551, most of the work sits in the spec sheet rather than in the pattern. Sizes up to 6/0 are inside our current treble range. Send the size list and the finish requirements, and we will come back with a diameter band per size and a sample plan for the first lot.