OMM Core T-Shirt A lightweight, insulative garment, the Core T-Shirt uses PrimaLoft ACTIVE technology, providing you with a great standalone or layering piece depending on the training conditions. Utilising PrimaLoft ACTIVE technology, the Core T-Shirt keeps you warm and cosy on the trail, and at just 75g/m2 keeps the garment lightweight. PrimaLoft ACTIVE has exceptional air permeability, meaning it can be worn alone and will shed excess heat, to prevent you from becoming too warm, however when worn with another layer the heat is trapped close to your skin, to keep you cosy in cold conditions. This will allow you to control the temperature during varied output and changing conditions. PrimaLoft Active is warmer, yet less than half the weight of a conventional fleece product, with down-like performance when dry, and performing well when wet. Due to its lightweight nature, the single-weight structure, allows you to pack down the garment well, without any excess bulk