Back Flush Seal Choices

I am installing a Gerber 21-310 back outlet toilet. It came with a Harvey's No-Seep No.3 urethane wax toilet bowl gasket with polyethylene flange.
http://www.wmharvey.com/prod/cat3/noseep/no3.php
Will this do a good job or is there something better? Would a FERNCO Wax Free Toilet Seal Work?
http://www.fernco.com/plumbing/w
It's flexible molded PVC. The box doesn't say anything about back flush applications.

Thanks.

ring

You DO NOT want to use a wax ring with a "funnel". You need one with a felt menbrane inside it, which WILL be marked "for use with wall hung toilets", which is the same as yours, or "for use with rear outlet toilets. I personally prefer the sponge rubber rings for that application, rather than wax ones.

Recommend?

Thanks hj. Can you recommend any name brands/model #'s that you know work?