This is the N Scale Straight Roadbed Expansion Track Section - Unitrack - 3 - 4-1/4'' 78-108mm by Kato USA inc.
This modular track system features nickel-silver rails fully integrated to a remarkably realistic-looking roadbed. The patented Unijoiners (included) lock the track sections together firmly and evenly. The frustration of derailments resulting from uneven rail joints and separating sections is eliminated.
There's no need to glue down cork roadbed; tack down track sections and file rail connections smooth after soldering. Simply snap it together and you're ready to go.
Telescoping track section expands from 3" to 4-1/4" 78 to 108mm.