FSA No.57-1 Orbit 1.5 ZS Tapered Headset Reducer w/Top Cap. Model : NO.57-1 Orbit 1.5 ZS. Fits tapered head tube: 50mm OD (upper) / 62mm OD (lower), with 1-1/8" (28.6mm) straight steerer fork. For tapered head tube: 50mm OD (upper) / 62mm OD (lower).
eBay