From the publisher's site:
The new Wings of Glory® game mats are a modular system designed to provide you with the ultimate gaming surface for your aerial battles, suitable both for WW1 and WW2 gaming.
Wings of Glory game mats are printed in full color on an extra-thick foam covered with special tissue. They can be rolled up for easy storage and will remain perfectly flat when opened. Each mat is 68 x 98 cm (27” x 39”) in size.
Different styles are available, each of them compatible with all other Wings of Glory Game Mats. You can join two, four, or even more, Game Mats together, in the combination you prefer, to create a larger battlefield.