Every propeller on a bill of materials is described by three numbers, and a drop-in replacement has to match all three plus the hub. This is what each one means, why 5 and 5.1 are different sizes, and what the rest of a part number is telling you.
Reading 5×4.3×3
Diameter × pitch × blades, all in inches except the blade count. A 5×4.3×3 is a 5-inch-diameter propeller with a 4.3-inch pitch and three blades. Manufacturers write the same thing as 5043, 5×4.3×3, or 5043-3, and some fold the blade count into a suffix. The numbers are what matter; the punctuation is house style.
Diameter
Tip to tip, in inches. Diameter sets how much air the propeller works with and what frame it physically fits: a 5-inch prop on a frame cut for 5-inch is a design decision made at the airframe, which is why the diameter is the one number nobody changes casually.
Pitch
The distance the propeller would advance through the air in one revolution if it slipped not at all, in inches. Higher pitch moves more air per turn and loads the motor harder; lower pitch turns faster for the same power and is easier on motor and battery. Pitch is the number tuning lives on. Two propellers of the same diameter and blade count but different pitch fly differently, which is why a 5×4.3×3 and a 5×4.5×3 are not interchangeable on a tuned platform.
Blade count
Two blades are the most efficient per unit of power; each added blade trades some of that efficiency for grip and smoothness at the same diameter. Tri-blades dominate 5-inch FPV for that reason; bi-blades reappear on long-range and folding platforms where cruise efficiency matters more than response. The line carries both: tri-blades in the fixed sizes, and a folding family quoted with a 2-blade or 3-blade coupling.
Why 5 and 5.1 are different sizes
A 5.1-inch propeller is 5.1 inches across, not a rounded 5. Many freestyle and racing families are 5.1-inch parts, and a 5-inch frame that clears a 5.1 has been designed to. The line's 5-inch family is the 5.0×4.0×3 (ANV-P5040), written with the decimals so the two are never confused; 5.1-inch sizes are quoted as programs.
CW, CCW, and sets
A multirotor's propellers spin in alternating directions to cancel torque, so each size is molded in a clockwise and a counter-clockwise version. Rotation is an ordering detail, not a separate size: parts are sold as sets of four — two CW and two CCW — or as pieces of a single rotation. In the Anvil line, rotation is an ordering suffix on the same part number.
Tip shape and planform
Bullnose tips carry chord all the way to the end of the blade and give a tri-blade the grip freestyle and tactical platforms want; pointed tips shed chord toward the end and are quieter and more efficient at cruise. Stub tips, squared off with a rounded corner, sit between the two. The planform — how the chord changes from root to tip — is where most of a propeller's character lives, and it is why two parts with the same three numbers from different makers do not fly identically.
The hub is the fourth number
Most 5-inch and larger propellers mount on a 5 mm motor shaft through a 5 mm bore, secured with an M5 nut. Micro sizes use a T-mount instead: a 1.5 mm shaft with two screws at 5 mm hole spacing. Every family in the line is a 5 mm bore; T-mount and other hubs are quoted as programs. A propeller that matches diameter, pitch and blade count but not the hub is not a drop-in, which is why every family in the line lists its hub interface.
What "drop-in" means in the line
Drop-in means same diameter, pitch, blade count, and mount. Each family in the line is built to a size class on all four, so a platform keeps its tune when the supplier changes. See the ten families, or send us the part number you fly and we will confirm whether one of them is the right class.