There is no absolutely canon reference to exactly what a Peregrine is. However, it seems that the Peregrine is a relatively small, lightly armed craft used as a fighter in the Trek universe. We have seen them used in "A Time to Stand", where several accompanied the battered Federation fleet seen at the beginning of the episode. We have also seen them in "Sacrifice of Angels", where Sisko launched many waves of fighter attacks at the Cardassians as the beginning of the "Valley of Death" battle to retake Deep Space Nine. These ships are small, but no concrete size has been established - if the cockpit module can only just hold one person then the overall length could be as low as 10 metres! However, most sources give a figure in the region of 30 metres for the Peregrine. This seems high to me; I drew a stick outline of a person sitting in the cockpit, and it gave me a length of around 15 - 20 metres. I've settled on 18 m as a compromise, but if anybody knows of an official length - or any other official figures - I'd love to hear about it.

Ships which have often been misidentified as Peregrines include the ships seen in "Preemptive Strike" and Chakotays vessel as seen in "Caretaker". These are not Peregrines, but are apparently two variants of the "Raider" type ship. Just to add insult to injury, the Star Trek Encyclopedia II puts a side-picture view of a Peregrine under the "Academy Trainer" entry. They have even added academy logos to the ship!

This is one of the larger mistakes in the Encyclopedia. We don't get many terribly good views of the Academy trainer in the episode, but if you look at the image on the "Trainer" entry of this site, and compare it with the size comparison view on the Peregrine page, you can see that they are nothing alike. Rick Sternbach is also on record as confirming the Encyclopedias mistake.