You will receive :
2 off 3.2mm x 8mm copper closed end rivets
2 off brass screws
1 off perspex "glass" window
1 off rubber type gasket.
This Sight Glass Seal Kit is the cheapest way to repair/ renovate your Water Level Sight Glass. Basically, if you don't need the brass surround, you can save yourself some money compared with the full assembly price.
If you don't have screws securing the assembly to your boiler, then you'll have to drill out the rivets using a 3mm drill bit. Using a hand help rivet "gun" you will secure the assembly back onto the boiler.