This is a pair of Boom Racing 2-stage foams for 1.9" x 4.19" RC crawler tires. They are two stage foams, outside is open cell and inside is closed memory cell.
Specification:
Outer Firmness: Soft
Inner Firmness: Hard
Size:
Open foam: 103.0mm x 36.5mm
Close foam: 74.0mm x 29.5mm
Includes:
2x 4.19" 2-Stage Foam Soft Outer / Hard Inner
Package total weight: 30.00 grams (incl. packaging)
Package size: 11.00 x 22.00 x 4.00cm
Factory description: Boom Racing 1.9 Dual 2-Stage Open (Soft)/Close (Hard) Cell Foam Insert for 4.19in (106mm) RC Crawler Tires (2)
Manufactured by Boom Racing
Manufacturer number: BRTR29000SH