I own both the large and the small Chessex square-grid battlemats. They have been a staple of my group's d20 campaign as much as our Player's handbook. The larger mat has a higher price tag, but offers more room to illustrate floorplans, accommodate more miniatures or counters, and move around. We found the smaller mat somewhat cramped for scale when larger encounters were involved.

Construction:
The Chessex mats are constructed from laminated vinyl with an overlying black square grid. The underside is rougher to provide a better grip on the tabletop, especially valuable if you're playing on a glass or other extremely smooth surface. Chessex mats have a great deal of durability if you maintain them well. They do not rip or tear easily, and their surfaces are quite forgiving to mechanical pencils or pens poking through paper.

Maintenance:
Each mat comes with instructions on how to care for it and they shouldn't come as a surprise. Always use water soluble markers (overhead markers) on the mat; dry erase markers will leave permanent lines you cannot erase. I also advise against using purple, yellow or red markers because these dyes have a habit of staining the vinyl if left on for extended periods of time. A purple outline in the corner of my mat stayed on for one gaming session and when I tried to clean it off at the end of the night, the ink bled in.

Cleaning the mat usually takes only a squirt of water from a spray bottle and paper towels. If you have particularly heavy ink or find the colour is sticking to the vinyl, try applying solution of heavily diluted white vinegar or alcohol.

Cost:
The mats were not cheap in Canada; they cost between $20 and $40, depending on size. However, they make a good investment for any groups which make regular use of grids for their campaigns. The mats are much easier to use than Dwarven Forge dungeon sets and they store well.

Extra:
Chessex mats are just about the perfect size for most miniatures and they fit Fiery Dragon's Counter Collections wonderfully. The spell templates provided in recent Dragon magazines can be applied cleanly as well.