The Matrix boasts a load of features for the money. For starters, it's a great poly fabric in a technical lightweight mesh weave.
The side panels and underarms are an even lighter, airier mesh. There's a deep front zip for good ventilation, fully backed by fabric so it doesn't rub against your skin. Pockets are on the small side but perhaps one of the best features is its reflectivity - a funky pattern by day, catches car headlights by night. The medium is cut close to the body.