Each Grubs Boot is hand finished and the boot uppers are made from a material called Chloroprene. It is a high-grade neoprene material that is commonly used and most recognisable for manufacturing wetsuits.
Starting from outside, the boot upper features a stretchy band that reduces the flow of cold air going inside the boot ensuring your foot stays warm at all times. To protect the neoprene material from snagging, layers of rubber are bonded to the neoprene that also forms an extremely stable and watertight structure. Depending on the intended use of the boots, the thickness of the insulating material comes in 5mm or 8.5mm, with the thicker layer being ideal in lower temperature areas. As you look inside the boots you will find a layer of mesh material that forms a barrier between you and the neoprene that traps pockets of air to help with the insulation. The boots also come with a 6mm removable inner sole that provides excellent cushioning and insulation.
It should be noted that although neoprene uppers allow a degree of stretching to accommodate wider calves, the thicker and higher the outer rubber protection, the firmer the uppers become.
HEXZORB™ TECHNOLOGY FOR SHOCK ABSORPTION
A hexagonal shock-absorbing component is directly molded into the heel of the outsole, to dissipate shockwave traveling up through the wearer's leg.
European Specifications and Grubs Safety Boots
There are European specifications that cover the construction of Safety Boots and Professional Use Boots (do not require toe protection).
Slip resistance will vary with different sole patterns. The pattern is determined by the intended use of the boot. Therefore, a boot with deep lugs on the sole will be great for use in muddy fields, but not very good on hard surfaces. Inevitably there will need to be compromises made where the intended use is a mixture of filed / hard surface.
Grubs tend to use a slightly softer material for the sole than some other manufacturers, but this slightly softer material will also provide slightly better slip resistance than a harder sole. This means the Grubs deep lug sole will provide slightly better grip on hard surfaces than a deep lugged sole from some competitors.
To test for waterproofing, all Grubs Boots are air tested twice using a machine that forces air into the boot at 10 psi - this process is undertaken when the neoprene boot is vulcanised to the sole and again when the outer rubber protection is applied.
The outer protective rubber layer is made from a blend of rubber and other materials (trade secret I think, or at least something quite scientific). This ensures the material is capable of the repetitive creasing and is also resistant to UV degradation.