Double sided with a recessed cleat.
Specific brand/type of this type is more of a personal preference. Models include, but are by no means limited to:
Eggbeater
Shimano mountain (i.e. M520)
Time ATAC
I used M520 for 2yrs. and they are fine, no reason not to use them
I use ATAC XS now, which are also fine.
I've tried eggbeater which are also fine.
The distinction between them is more subtle than you may come to believe when reading about pro/cons from fanatics.
Al