From Lexicanum

All Space Marine Chapters make use of ships known as Rapid Strike vessels, used primarily for patrolling Space Marines domains and providing an escort for Battle Barges and Strike Cruisers. Rapid Strike vessels are crewed by Chapter serfs, overseen by a cadre of Techmarines and other specialists.

Due to their age and small size, each chapter has come up with variants to suit their own needs. This means that they come in a vast variety of designs, the three most well known being:

• Gladius class Frigate
• Nova class Frigate
• Hunter class Destroyer

They also make use of the more common, but slower Imperial Frigates and Destroyers:

• Firestorm class Frigate
• Sword class Frigate
• Cobra class Destroyer

They are relative in size to an Imperial Frigate or Destoyer, and usually carry between 20-50 Space Marines. Rapid Strike Vessels are deployed when devoting an entire company of Space Marines would either be too slow or tactically unnecessary.

Rapid Strike vessels don't tend to survive long enough in a fight to earn a name for themselves due to their small size and general fragility, but are still very common throughout the Space Marine fleets.