Types
LeatherTraditional leather saddles, such as those made by Brooks, have been used for many years. Leather saddles are generally comfortable after a break-in period.
PlasticMost modern bicycles are fitted with a plastic saddle. The
base of the saddle is made from a molded piece of plastic and fitted with metal rails to allow the saddle to be attached to the seat post.
There is generally some form of padding on top of the plastic
base, consisting usually of closed cell foam and then a fabric cover.
Groin Safety
While riding an upright bicycle improves the cardiovascular system and can actually improve the erectile function among men, riding a bicycle for prolonged periods of time with a poor cycling technique can still cause problems for both men and women due to a reduced blood flow in the crotch area.
A sign of these problems can sometimes be a tingling sensation in the area when stepping off the bicycle after a ride, as blood flow surges back into the area again. This issue is more related to the cycling technique than the saddle type, although there are special, more anatomically correct designs to relieve crotch pressure as well. Examples of such designs include the cutaway saddles and noseless saddles. Cutaway saddles are similar to regular saddles in their design, just with the middle part cut out to reduce pressure on the perineum among men. Noseless saddles are basically two separate saddles next to each other, with one smaller "saddle" per buttock. Such saddles achieve a similar relief of pressure by using a different design.
Some useful techniques to reduce crotch pressure while cycling include:
1) Ensure your saddle is horizontally aligned. If the front is aligned too far upwards it will increase the perineum pressure, while a downwards alignment will reduce the sit bone support of your pelvis, again resulting in an increased perineum pressure.
2) Make it a habit to stand up occasionally during your ride.
3) Adjust how you sit from time to time.

Seat Post
A bicycle seatpost is an adjustable tube that extends upwards from the bicycle
frame to the saddle. It is made of steel, aluminum, titanium, or carbon fiber. The size of the seatpost is dependent upon the internal dimensions of the seat tube of the bicycle
frame. They come in various diameters, lengths and offsets. Offset is the distance between the centerline of the seatpost tube and the centerline of the clamp area.
Seatposts generally clamp onto saddle rails.