What side length can make a triangle with side lengths of 6 and 6?

I am not sure what you are asking but I will give you as much information about this triangle as I can and you can ask me whatever you want to about it. 

Equilateral triangle.Sides: a = 6   b = 6   c = 6

Area: T = 15.588
Perimeter: p = 18
Semiperimeter: s = 9

Angle ∠ A = α = 60° = 1.047 rad
Angle ∠ B = β = 60° = 1.047 rad
Angle ∠ C = γ = 60° = 1.047 rad

Height: ha = 5.196
Height: hb = 5.196
Height: hc = 5.196

Median: ma = 5.196
Median: mb = 5.196
Median: mc = 5.196

Inradius: r = 1.732
Circumradius: R = 3.464

Vertex coordinates: A[6; 0] B[0; 0] C[3; 5.196]
Centroid: CG[3; 1.732]
Coordinates of the circumcenter: U[3; 1.732]