FRENTE A FRENTE means face to face. It works similar to the original version of Rueda llanta, with to circles inside each other, and default partner change in the grande circles. There are no pequeña circles, but the circles connect on certain figures, like amistad, tome electrica, etc.
Also, the couples may switch circle by travelling in between each other and turn around.
For this to work, you need an even number of couples. It’s not well suited for social use, because one more couple on the fly will destroy the structure. For social use a Rueda combo with two circles is more suitable.
Rueda frente a frente
This structure was introduced at SalsaNor’s Rueda Congress 2013 in Southampton. It is not very much in use, instead for similar use Rueda llanta or Rueda combo is often preferred, depending on the social angle.