In general the Semi QH Bar will fit the smaller build horse. The Quarter Horse bar or medium tree will fit the average build horse under 1050-1100 lbs. The FQHB (Full Quarter Horse Bar) or Wide Tree should fit the large build horses over 1050 lbs. The Extra Wide or Haflinger should fit the quite round, large mutton wither horse over 1300 lbs. The Draft Horse should fit a horse that is over 1500lbs. Read more.

Tree traits: Wood Rawhide/Bullhide Covered - very strong and heavy. Wood Fiberglass Covered - very strong and heavy. Ralide - lighter weight, economical and not same strength as a wood tree. Flex - Lightweight, can be expensive, comfortable and not designed for the rigors of ranch/farm work. Read more.

A general guide for western saddle seat sizes: Women:
Saddle Seat Size (Western) 15" Weight 105 to 150 Pant Size 6 to 10
Saddle Seat Size (Western) 16" Weight 150 to 170 Pant Size 10 to 14
Saddle Seat Size (Western) 17" Weight 170 to 210 Pant Size 16 to 20
Saddle Seat Size (Western) 18" Weight 210 + Pant Size 22 +
Men:
Saddle Seat Size (Western) 15" Weight 130 to 160 Waste Size 29 - 34 inches
Saddle Seat Size (Western) 16" Weight 160 to 190 Waste Size 31 - 36 inches
Saddle Seat Size (Western) 17" Weight 190 to 230 Waste Size 38 - 42 inches
Saddle Seat Size (Western) 18" Weight 230 + Waste Size 42 + inches

Read more.

Grainout or Leather:  This seat is easy to maintain, is smooth and wipes clean and repels water.

Roughout or Suede:  This seat has the neat suede look, is softer to the touch and provides a more secure fit.

Padding:  Most trail, show, barrel, roping, reining, endurance and cutting saddles have padded seats, though many cutting saddles have very little to no padding.  Many ranch saddles and some cutting saddles have no padding.  

The cantle is the upright part at the back of the seat of a western saddle.   The cantle provides support for your lower body and also comfort while riding.    Roping saddles usually have a lower cantle (3 to 3.5") making it easier to lift your leg over the saddle when dismounting.   Trail and reining saddles usually have a medium height cantle around 4-5"" and Barrel Racing and Ranch saddles often have higher 5" cantles.  

The swell is the widest distance from the outside ends of the fork - it is the part of the saddle that the horn is on top of.  A wider swell will give you more leverage and security where the narrow  swell will give you more room to maneuver your legs. 

Different riding disciplines use horns differently.  A trail saddle usually has a horn easy to grab hold of where a roping saddle has a reinforced horn that is thicker and with a larger cap.  A show saddle usually has a low ornate horn. Read more.

There are two main aspects to rigging: position and hardware

Position:  Can be Full, 7/8, 3/4 or Center Fire.   The 3-way rigging gives the option for Full, 7/8 or 3/4.  Click on the link below for more information on rigging.

Hardware:  This determines the strength (and also bulk) of the rigging.  Often Rope and Ranch saddles are double rigged directly to the tree, where most other saddles use in-skirt rigging. Read more.

Round or Square:  Many short backed horses require shorter skirting.  The round skirts do not extend down the same that a square skirt does and provides relief for short backed horses.

Length:  Most saddles have skirt lengths ranging from 24.5" to 28"  This is a general skirt length given as a 14" seat will have a longer skirt than the same model with a 17" seat.

Close Contact:  Some saddles have butterfly type skirting that is cut-out a bit behind the fenders.  This allows the rider to have closer contact with the horse being able to give better cues.  

The shape of stirrups are usually bell, oxbow (round) or square (aluminum trail/endurance).  They also can be wrapped in leather or the stronger rawhide.  Some saddles come with the option of having oversized stirrups for the larger boot. 

Most leather saddles weigh between 25 lbs. and 42 lbs.  Often the tree determines much of the saddle weight along with the rigging used.  If the saddle has a back cinch and leather tie straps and off-billets the saddle weight will be several pounds higher.