Kraig Biocraft Laboratories Inc (KBLB)

[first mike]

The strength of spider silk is highly variable. It depends on many factors including kind of silk (Every spider can produce several for sundry purposes.), species, age of silk, temperature, humidity, swiftness at which stress is applied during testing, length stress is applied, and way the silk is gathered (forced silking or natural spinning).[32] The value shown in the table, 1000 MPa, is roughly representative of the results from a few studies involving several different species of spider however specific results varied greatly.[33]"

But we are not talking about the average strength of six or more completely different types of spider silk as produced by the many different spinning organs on various parts of the bodies of hundreds of different species of spider.

We are talking about the breaking strength (Height of the Stress/strain curve) and elasticity (horizontal length of the S/S curve) and toughness (area under the S/S curve) of the Drag Line silk of the Nephilla Clavipes spider.

And its numbers are:

Maximum stress (MPa) 664.6 @ standard deviation 60.5
Maximum strain (%) 19.7 @ standard deviation 4.8
Break stress (MPa) 658.1 @ standard deviation 59.2
Toughness (MJ/m3) 79.6 @ standard deviation 25.4

as given in the PNAS article.