This is Stihl's Rollomatic ultra light 18" chain guide
Brand, model, ID: 1018 - 3/8 .050 - Stihl: 3003 000 7817 - 795711288792
Characteristic: Consists of three arc welded plates, high stability at low weight, robust.
Suitable for chain: 33RS 66E
For models: 029, 034, 036, 036, 038, 039, 042, 044, 045, 046, 048, 056, 064, 066, 290, 291, 310, 311, 340, 341, 360, 361, 362, 380, 390, 391, 440, 441, 460, 461, 640, 650, 660, 66, E20, E220