Eric's extension is a Mills mess variation invented by Eric Uhrhane. Instead of changing direction every 3 throws like the normal Mills mess, this pattern changes direction every 5 throws.
After a normal under the arm throw, the arms keep moving around each other in the same direction so that they cross again, wrapping all the way around each other so the right hand is to the right of the left hand again while the arms are crossed. The next throw is different kind of under the arm throw: if it's a right hand throw, the right hand is reaching under the left arm from left to right instead of from right to left.
After that throw, the pattern changes direction in the same way as Mills mess, except the arms are still crossed twice. The arms stay wrapped around until the hand that just threw makes its next catch in the same position, and then during the next throw the arms start uncrossing.
My Extensions.wmv
Eric's extension with 3 balls, 4 balls, and 3 clubs by Mats Riasatian
Chris Hodge's Eric's Extension Tutorial
Eric's extension tutorial
3 BALL JUGGLING Sumita's Scream(Triple Mills Mess)
Sumita's scream by Hideki Sumita - a 7-beat version of Eric's extension, with the arms crossing three times