A while back I contacted Ice Halo about the difference in protection between halo and halo HD, This is an excerpt from the attachment they sent (Their certification):
The Ice Halo Protective Headband and the Halo HD will help provide protection around the head in the event of a fall. No product, including the Ice Halo or a helmet, can completely prevent concussions or serious injury in the event of a serious impact to the head.
The Ice Halo and Halo HD were tested according to: CSA Z262.1-09 (April 2009) Annex A, Hockey Helmet Standard which is equivalent to ASTM Worldwide Standard. The Impact Drop Testing was performed by Biokinetics and Associates Ltd., Ottawa. Biokinetics is one of the top impact testing facilities in the world. This standard allows a maximum impact of 275 G with a helmet.
The results of the testing provided the following information:
Measured impact with no protection was:
to the side of the head: 393.8 G average
to the front of the head: 296.6 G average.
Measured impact with an Ice Halo:
the side of the head reduced to 220.5 G average
front of the head was reduced to 201 G average
Measured impact with a Halo HD:
the side and front of the head was reduced to 211 G average
Total impact to the front of the head was therefore reduced by at least 95.6 G average and reduced by at least 173.3 G average to the side of the head, compared to no protection. The Ice Halo passes the hockey helmet standard for side and front impact, which allows a maximum impact of 275 G with protection. The Ice Halo and Halo HD are the same density all the way around the head; it is the point of impact which creates the minor variance in the averages.
There is no CSA standard available for protective headband testing; they must be tested against the above Hockey Helmet Standard. Therefore no protective headband can claim to be CSA or ASTM approved or “passed by the CSA or ASTM”. Protective Headbands do not have the hard outer shell, a ‘top’ or a chin strap and therefore cannot be given a “pass” certification. We can provide a video of the Ice Halo being tested by Biokinetics upon request. The Ice Halo Ltd. team is part of the ASTM International Worldwide Standards Sub-committee team currently working on developing a stand alone standard for protective headband testing
I assume the difference between the two in terms of protection are marginal, but perhaps someone with a physics background could comment. In the accompanying email they said the halo HD was slightly more protective. Re buying the correct size being critical, Maybe contact them?