A gambeson is perfect for wearing under your armor.
It provides plenty of padding and airflow so you stay comfortable in your armor.
It is designed to be worn under chainmail, a full suit of armor,
or individual pieces of armor,

The Gambeson is built of fine quality cotton fabric. When worn by itself it is comfortable to wear.
Gambeson is produced with a sewing technique called quilting.
Aketon lagging Armor. When worn by itself it is comfortable to wear.
Lagging Chausses Lower Under Gambeson Hauberk Medieval Armor

Small # Chest-37" Length From Shoulder- 33"
Medium # Chest-41" Length From Shoulder- 34"
Large # Chest-44" Length From Shoulder- 34"
X-Large # Chest-47" Length From Shoulder- 34"
2X-Large # Chest-50" Length From Shoulder- 34"
3X-Large # Chest-54" Length From Shoulder- 34"

Other size also avealable

4X-Large # Chest-56" Length From Shoulder- .36"
5X-Large # Chest-58" Length From Shoulder- 36"
6X-Large # Chest-60" Length From Shoulder- 36"
7X-Large # Chest-62" Length From Shoulder- 36"