MCS keeps a complete inventory of parts & accessories for your law enforcement helmets.
The shape of your head has as much, if not more, to do with your helmet size as the size of your head does. Contact Bob Cook to assist you with obtaining the best fit possible. Arai offers its law enforcement helmets in 7 helmet sizes from XSm through XXXLg, 13 liner sizes and 7 ear cup sizes.
| Helmet Size | Liner | Ear Cup |
| XSmall (6 ½ - 6 5/8) (53-54cm) | II-10mm | 30mm |
| Small (6 ¾ - 6 7/8) (55-56cm) | II-7mm | 25mm |
| Medium (7 - 7 3/8) (57-58cm) | III-10mm | 25mm |
| Large (7 ¼ - 7 3/8) (59-60cm) | III-7mm | 20mm |
| XLarge (7 ½ - 7 5/8) (61-62cm) | IV-7mm | 20mm |
| XXLarge (7 ¾ - 7 5/8) (63-64cm) | IV-5mm | 15mm |
| XXXLarge (8 - 8 1/8) (65-66cm) | Available only in Classic-LE and SZ/m models | |