Rubber knee-protectors are definitely tough and long-wearing because they are resistant to abrasion and aggressive chemicals.
Plastic knee-protectors made of thermo-plastic elastomers are an inexpensive alternative – they have similar properties to rubber but are not so long-wearing.
All models are padded with cellular rubber. This is a soft material which absorbs no moisture, remains permanently elastic and provides good pressure distribution.
PUR knee-protectors are moulded in one piece, they are very light and are mostly used in the DIY sector.