Serpentine channel / Microreactor, 20x50µm, 342mm length

When should I use the spacers?
The metal strips are used for thin bottom chips and are also part of the holder for resealable flow cell's.
This are currently the following products (list might be incomplete): SKU SKU old Description Note 11000746 00746 Fluidic Connect Pro for resealable flow cells Normally already pre-assembled  11000746 00745 Insert set for resealable flow cells   11003133 03133 Thin bottom flow cell    11106327 03133-F Thin bottom flow cell - coated   11003196 03196 Thin bottom flow cell - 0.5mm   11006345 03196-F Thin bottom flow cell - 0.5mm - coated   11003164 03164 Thin bottom flow cell - 1.5mm   11006338 03164-F Thin bottom flow cell - 1.5mm - coated   11003694 FC_R50.332.3_PACK Serpentine channel / Microreactor, 20x50µm, 342mm length   11003644 FC_R50.332.3-F Serpentine channel / Microreactor, 20x50µm, 342mm length - Coated   11003040 03040 Serpentine channel / Microreactor, 45x140µm, 350mm length     11006834 03040 - F Serpentine channel / Microreactor, 45x140µm, 350mm length - coated   11006722 FC_X3550CH.3_PACK Cross channel chip - thin bottom   How to apply the spacers? The spacers are placed beneath the top insert, as shown in the picture below. What should I do when I don't have spacers available?
Just contact us to request new spacers.

Wet etched structures are extremely smooth and have a roughness in Angstrom range. The structures are fully optical transparent. 
Large roughness for structures in glass chips is typical observed for structures manufactured by use of laser assisted manufacturing techniques or abrasion-based techniques like powder blasting. Almost all catalogue products from Micronit are manufactured using wet etching to create full transparent channels without substantial roughness.