A heated glove is a finished product. A heated liner is a component the customer wears against the skin and then covers with something else. It changes every dimension on the tech pack, because a liner that does not fit inside the shell is not a slightly worse product, it is an unusable one.

A liner is sold on fit, not on heat

Category listings describe liners as thin enough to wear inside gloves or mittens the customer already owns, and that is the entire proposition. If the liner adds bulk at the knuckles or bunches at the palm, the outer glove stops fitting and the liner gets left in a drawer.

So the first specification line is not wattage. It is the finished thickness at the palm and at the finger joints, measured on the assembled liner rather than on the fabric.

Why most liners fail under a shell

Three failure modes account for most complaints, and none of them is electrical.

  • Bunching at the palm when the hand closes, because the liner was cut to a flat pattern with no allowance for the change in circumference.
  • Riding down at the wrist as the outer glove is pulled on, because the cuff is too short to anchor under the shell's cuff.
  • Seam ridges under the element, which the wearer feels as pressure rather than warmth, especially when gripping a pole, a tool or a handlebar.

All three are pattern and construction decisions, and all three are checkable on a sample by putting the liner inside the intended shell and making a fist.

Touchscreen on one finger is not touchscreen

Published glove reviews are consistent on this point: touchscreen compatibility is frequently limited to the index finger. On an outer glove that is a compromise the wearer can live with. On a liner it is close to useless, because the liner is worn under another glove and the outer glove is what actually touches the screen.

That leads to a decision worth stating explicitly. A liner can be conductive at the thumb and index for wearing alone indoors, or across the fingertips for use under a conductive outer glove. The second is the more useful configuration and the harder one to specify, because conductivity has to survive the liner's own washing without the coating cracking at the flex point.

The battery belongs at the wrist

Liner batteries are small enough to sit on the back of the wrist, and that position is not arbitrary. A pack on the palm interferes with grip. A pack on the back of the hand interferes with the shell. The wrist is the only area that stays clear of both.

Two details matter once the position is fixed. The pack must sit off the wrist bone, not on it, or the wearer feels it within minutes. And the cable run from the pack to the element has to be short enough that it cannot catch when the hand rotates, which usually means the pack is placed on the same side as the element entry point rather than opposite it.

Reviews of outer heated gloves repeatedly note that runtime falls sharply on the highest setting. The same is true of a liner, and it is the honest way to quote performance: a runtime figure is only meaningful against a named pack and a named setting.

Element thickness is a dexterity decision

In a glove, element thickness is a comfort issue. In a liner, it is a function issue, because the wearer is operating something with two layers on. A wire that reads as soft in a 3 mm glove reads as a ridge in a 1 mm liner.

The practical check is not a number on a drawing. It is whether the wearer can pick up a coin, work a zip and hold a pen while wearing the liner inside the shell. Put that in the approval criteria, so the sample is judged on the task.

Sizing and laundering

Sizing a liner is not the same as sizing a glove. It is worn against the skin, so it needs a closer fit, and the outer glove adds its own allowance on top. Quoting a single size band against glove sizes invites returns, because the customer's outer glove size tells you very little about the hand inside it.

Washing is the other overlooked line. A liner is washed far more often than an outer glove, and it is washed with the electronics detached. The element and its connector have to tolerate that cycle count, and the care instruction has to describe one sequence, consistent between the label and the insert.

Specification lines before sampling

  • Finished thickness at the palm and at the finger joints, measured assembled
  • Pattern allowance for the change in circumference when the hand closes
  • Cuff length that anchors under the intended outer shell's cuff
  • Seam placement away from the grip surface
  • Touchscreen coverage: thumb and index, or all fingertips — stated, not implied
  • Battery position off the wrist bone, on the same side as the element entry
  • Cable run short enough not to catch on rotation
  • Runtime quoted against a named pack and a named setting
  • Wash cycle count with the electronics detached

A liner that meets these is unremarkable to wear, which is exactly the goal. The customer should notice the warmth and nothing else.