Will any intercom fit my helmet?

Mostly yes, because they clamp or stick rather than bolting to anything. What decides whether it is bearable is speaker depth, published in millimetres — and shallow ear pockets are the most common reason an intercom is uncomfortable.

The recess to measure inside your own shell

The depth of the recess in each cheek pad where the speaker sits. Makers publish speaker thickness, and a speaker deeper than the pocket presses on the ear for the whole ride. No amount of repositioning fixes it, and it is the single most common complaint in the family.

How they attach

A clamp that slides between the shell and the lining, or an adhesive plate. Clamps are removable and need a gap; adhesive works where a clamp will not fit and is effectively permanent. Some helmets are sold prepared, with a recess moulded for a specific system — that is published and worth knowing.

The microphone, which has two forms

A boom arm for open-face and flip-up helmets, and a wired patch for full-face helmets where a boom will not fit past the chin bar. Most kits supply both; a few do not, and on a full-face that matters.

What does not travel between brands

Pairing across different makers works for basic calls in most cases, and the mesh networking that makes a group usable generally does not — that is a maker’s own protocol. If you ride with the same people, matching systems is worth more than any single feature.

The figure with a condition attached

Range. It is measured in open ground, between two units, with nothing in between — not in a line of riders behind a lorry. Makers publish the condition alongside the number, and reading both is the difference between a specification and a promise.