Components, as follows: 1. Mirrors cooled either by ‘active cooling’ or by heat pipe cooling; Technical note: ‘Active cooling’ is a cooling technique for optical components using flowing fluids within the subsurface (nominally less than 1 mm below the optical surface) of the optical component to remove heat from the optic. 2. Optical mirrors or transmissive or partially transmissive optical or electro-optical components, other than fused tapered fibre combiners and Multi-Layer Dielectric gratings (MLDs), specially designed for use with specified ‘lasers’; 3. Fibre ‘laser’ components: a. Multimode to multimode fused tapered fibre combiners having all of the following: 1. An insertion loss better (less) than or equal to 0,3 dB maintained at a rated total average or CW output power (excluding output power transmitted through the single mode core if present) exceeding 1 000 W; and 2. Number of input fibres equal to or greater than 3; b. Single-mode to multimode fused tapered fibre combiners having all of the following: 1. An insertion loss better (less) than 0,5 dB maintained at a rated total average or CW output power exceeding 4 600 W; 2. Number of input fibres equal to or greater than 3; and 3. Having any of the following: a. A Beam Parameter Product (BPP) measured at the output not exceeding 1,5 mm mrad for a number of input fibres less than or equal to 5; or b. A BPP measured at the output not exceeding 2,5 mm mrad for a number of input fibres greater than 5; c. MLDs having all of the following: 1. Designed for spectral or coherent beam combination of 5 or more fibre ‘lasers’; and 2. CW ‘Laser’ Induced Damage Threshold (LIDT) greater than or equal to 10 kW/cm 2 .