These are a Snowbird Main Ski (825) by Dubro.

Features

Torsion Bar Design
Easily mounts on airplanes with Dural or Wire Landing
Gear in about an hour
High density Black Polyethelene
Pre-Molded Runners
Ideal for .60 Size Airplanes

Includes

Two Skis
Two Torsion Wires
Two Torsion Wire Mounts
Two Pieces of Heat Shrink
Four 4-40x3/8" bolt
Four #4 lock washers
Eight Torsion Bar Nylon Mounting Blocks
Eight 2-56x1/2" Bolts
Eight #2 Lock Nuts

Requires

Mounting Hardware and tools

Specifications

Length: 228.6 mm (9")
Width: 63.5 mm (2.5")
Wire Diameter: 3.2 mm (0.125")