Do these hold up in direct sunlight, outside, exposed to the elements? What are the specs on using them outdoors to cover a grated staircase and landing for footing and stability? Also, do they become slippery when wet, i.e. rain?

Our 1/2" 4' x 6' Mega Mats can be used outdoors and will perform just fine in the elements. Since these mats are made from the same material as your tires, they won't be affected by rain, snow, or ice. The only thing you will notice with the mats is that over time they will fade in direct sunlight. These mats can be used as flooring over staircases. Since these mats are made from rubber, they are very slip resistant and are more slip-resistant even when wet.