SICK GRTB18-P2412V Photoelectric sensors. SICK GRTB18-P2412V is a photoelectric sensors in the GR18 family. SICK identifies this exact configuration as manufacturer article 1085749. The official technical record specifies Functional principle: Photoelectric proximity sensor; Functional principle detail: Background suppression; Dimensions (W x H x D): 18 mm x 18 mm x 73.5 mm; Housing design (light emission): Cylindrical; Housing length: 73.5 mm; Thread length: 49.3 mm. The linked SICK data sheet is specific to GRTB18-P2412V.