If your car has a tight cabin, and there is a risk of the helmet contacting the roll cage, get this low profile rollbar padding from Longacre.
Longacre Roll Bar Padding
Quickcar SFI 45.1 Roll-Bar Padding - 3' (Size: 1-5/8 to 2)
Roll Bar Bracket
Rollbar Padding
Longacre Roll Bar Padding 65162
Foam Roll Bar/Cage Padding, Set of 6, Black, 36 Inch
Roll Bar Padding - Pegasus Auto Racing Supplies
Foam Roll Bar/Cage Padding, Set of 6, Black, 36 Inch
Foam Roll Bar/Cage Padding, Set of 6, Black, 36 Inch
Rollbar Padding