Helmets meeting the following standards must be worn while on course:
All helmets meeting the latest or two immediately preceding Snell Foundation
standards (SA2015, SA2010, SAH2010, SA2005, SA2000, M2015, M2010,
M2005, M2000, K2015, K2010, K2005, K98); SFI standards 31.1, 41.1, 31.1A,
31.2A, 41.1A, 41.2A; ECE R22.05; FIA standards 8859-2015, 8860-2010, 8860-
2004; or British spec BS6658-85 type A are acceptable.
Full face or modular helmets shall be worn while competing in an open-wheel
car, formula car, or kart. Face shield, goggles, or similar face protection (conventional
eyeglasses are not sufficient) shall be worn while competing in any
other vehicle with less than the standard-size windshield.
Formula Junior drivers must use helmets meeting the above, SFI 24.1 (Youth
Helmets), Snell CMR2007 (Children’s Motorsports Restricted), or Snell
CMS2007 (Children’s Motorsports Standard) specifications. Also, Formula
Junior helmets must be of closed face design incorporating full face shields
and chin bars.
For maximum protection, helmets must fit securely and should provide adequate
peripheral vision. The chin strap must be securely fastened. Loaner
helmets should be available to vehicle occupants not having their own.
Disclaimer - I own Solo Performance and we sell helmets!
It is a little confusing...
If you have an open wheel car or kart, you have to wear full face. Everyone else can wear whatever they want, open or closed but if your windshield is not stock sized in a convertible, you would be required to have eye protection that you would want to have anyway.
A Snell 2010 would be good until the 2025 standard is released.
There are basically very few/no open face M rated inexpensive helmets. If you go M rated, you would want to go with full face. HJC CL-17 is one of our most popular and runs around $125-ish.
Some track events allow M rated and some do not. Personally, if I thought I might be going on track in the near future, I would probably step up to an SA rated helmet out of the gate and that way you are always covered. SA2015 Open face are around at $150-ish, $175 for entry level full face. There are still a few SA2010 closeouts available as well for very good prices.