These filters are available to narrow down your choices in the olympic bars category.
The thickness of the ~52" long middle section of the bar.
28mm - Olympic lifting (clean-and-jerk, snatch), deadlifts. Most have lots of "whip".
28.5mm to 29mm - Less whip. A good choice as an all-purpose bar.
30mm+ - Specialty bar for squats and presses. Some bars are this thick to make up for low strength steel (see Tensile Strength below)
The finish on the shaft of the bar.
Black Oxide - Good grip. Should be oiled regularly for high corrosion resistance. Very thin coating, so feels the most like a bare steel bar. Can wear off over time and is scratched easily on racks.
Hard Chrome - High corrosion resistance. More slippery when wet. Lasts indefinitely with no signs of wear. Little or no maintenance required.
Zinc - Medium corrosion resistance. Textured, chalky feel. Can wear off over time and is scratched easily on racks.
Stainless Steel - Not a finish, but type of steel. Highest resistance to corrosion. Little or no maintenance. Most expensive.
Cerakote - High corrosion resistance, available in a variety of colors.
The knurl depth is the depth (or feel) of the grooved pattern on the shaft that makes for a good grip.
Soft - For high reps of cleans and snatches where you want the bar to slide in your hand.
Medium - Best grip for an all purpose bar.
Aggressive - Painful. Good for max attempts with deadlifts, cleans and snatches.
Bushings - Best for most people. Spins just right without getting out of hand.
Bronze Bushings - Best choice. Very hard, won't break, lowest friction (best spin) against the steel sleeves.
Steel or Brass Bushings - Softer metal, higher friction.
Composite Bushings - Highest friction spin, least expensive. Still very durable.
Needle Bearings - Ultra-sensitive spin for cleans and snatches for experienced lifters.
The strength of the steel shaft, in pounds per square inch (PSI).
80,000 PSI - Approximate strength of the cheapest bars around $100.
130,000+ PSI - Relatively weak, but a step above the cheapest bars. Fine for most users.
180,000+ PSI - Minimum recommended for commercial use.
190,000+ PSI - Great strength, for any commercial environment. Recommended for heavy squats where it may be slammed onto a rack.
200,000+ PSI - Very strong. The best bars on the market.
The center knurl is the ~8" wide strip of knurling right in the center of the bar, surrounded on both sides by non-knurled areas.
Center knurl is most helpful for heavy squats, to help keep it on your upper back. It's also in the IWF spec, for competition rated bars.
Crossfitters often prefer no center knurl, to avoid scratching the front of their neck during high rep cleans.
1/2" wide finger guides towards the ends of the shaft in the knurl that the IPF and IWF organizations have specified.
IPF marks are 810mm apart. IWF are further apart, 910mm. Many bars have both, to help you place your hands symmetrically for a variety of exercises.