The tightest turn in the book. First radius is where OO layouts begin — at 371mm radius and 22.5° per piece, sixteen ST-220s close a full circle barely 75cm across, small enough for a tabletop, which is exactly why the inner loop of nearly every train set runs this geometry. Peco moulds it in Setrack's rigid unit style: solid nickel silver Code 100 rail integrally moulded into the sleeper base, an SL-10 metal joiner fitted at each end (swap in SL-11 nylon joiners for isolation breaks), and the same 371mm standard as Hornby's first radius, so Setrack and train-set curves mix freely in one oval.

The First Radius Rule

Know it before you buy: first radius is tight, and not all stock likes it. Short and mid-length locomotives, tank engines, four-wheel wagons and train-set coaches sail around happily; many larger RTR models — long-wheelbase steam, modern bogie coaches — specify second radius minimum in their instructions, and will bind, derail or overhang awkwardly on first. Check your stock's stated minimum radius: if it says second, build with the ST-225 (438mm) instead — and the classic double-track oval uses both, ST-220 inside, ST-225 outside, nesting at Setrack's standard spacing.

Grows With the Layout

Setrack is fully compatible with Peco's Code 100 Streamline range, so the first-radius circle that starts a layout never gets discarded — it becomes the storage yard curve, the industrial siding, the child's loop on a layout that's grown flexi-track ambitions. Straights (ST-200 on our shelves), points and the wider Setrack geometry all share the system.

Specifications

Brand: Peco
SKU: ST-220
Product: Setrack No.1 radius standard curve
Gauge / Code: OO (16.5mm) · Code 100 nickel silver
Radius / Angle: 371mm · 22.5° — 16 per circle
Joiners: SL-10 fitted both ends · SL-11 nylon for isolation
Stock Note: Larger models may specify 2nd radius minimum — check before building
Partners: ST-225 2nd radius (outer loop) · ST-200 straights