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Dunlop

Black Widow 18 (1.21)

Polyester Gauge 18 1.21 mm In production

Lab measurements for Dunlop Black Widow 18 (1.21), ranked against all 789 strings in the database. Every figure below is a testing-machine result at a fixed reference tension, not a playtest opinion.

Measured values

Stiffness

195lb/in

lower = softer, kinder on the arm

Tension loss

31%

lower = stays where you strung it

Energy return

90%

higher = livelier, more free power

Spin potential

5.8

higher = more spin off the string bed

Ball bite

0.571COF

higher = grabs the ball harder

Snapback

0.099COF

lower = strings slide and snap back

How it ranks against all 789 strings

Stiffness 195 lb/in · 63rd pct

Stiffer than 63% of strings tested.

Tension loss 31 % · 49th pct

Sheds more tension than 49% of strings tested.

Energy return 90 % · 60th pct

Livelier than 60% of strings tested.

Spin potential 5.8 · 76th pct

More spin potential than 76% of strings tested.

Ball bite 0.571 COF · 93rd pct

Grips the ball harder than 93% of strings tested — bites the ball hard through the brush.

Snapback 0.099 COF · 62nd pct

More string-on-string friction than 62% of strings tested.

Strings that play like this

Closest matches across stiffness, tension loss, energy return and spin potential.

Gamma IO 17 (1.23) 98% match Solinco Tour Bite Soft 16L (1.25) 96% match Solinco Revolution 18 (1.16) 95% match Gamma IO Soft 16 (1.28) 95% match Gosen Polylon Premium 16L (1.27) 94% match Tourna Black Zone 16 94% match

More from Dunlop

What these numbers mean

Stiffness · lb/in

How much the string bed resists deflection. Higher plays firmer and more controlled; lower plays softer and easier on the arm.

Tension loss · %

Share of the reference tension the string sheds under a fixed test protocol. Lower means the bed stays where you strung it for longer.

Energy return · %

Share of impact energy handed back to the ball. Higher plays livelier and more powerful.

Spin potential

Ball friction divided by string-on-string friction. Higher means better bite with a cleaner snapback, so more spin.

Ball bite · COF

String-on-ball friction. Higher grabs the ball harder through the brush.

Snapback · COF

String-on-string friction. Lower lets the mains slide and snap back into place after impact.

Compare Black Widow 18 (1.21) against 789 strings Find the right string for me