Most of all remember to consider if that specific breed will fit your lifestyle! It's a 10+ year commitment! Beautiful choice of dog breed by the way
They grow to
at least 21 inches tall shoulder height and weigh between 60–100 pounds. They are high energy dogs that need a minimum of two hours exercise/running every day! If he still has his balls and shows interest in sex he should be around average for that size dog. Anywhere from 5 to 7 inches long fully erect with a knot around 3 to 4 inches wide, about the size of a tennis ball or slightly bigger. There is a lot of variability, even within the same breed. If he's neutered he may still show interest and get an erection but lack of hormones stuns the well, size down there slightly.