Here at Apogee Components, we offer these types of tube couplers (also known as Airframe Couplers):

• Regular Apogee Couplers (Thin-wall)
  This is the same type of coupler you'd find in a standard Estes rocket kit. They are made from lightweight kraft paper that is very inexpensive. All these couplers have thin wall thickness to keep the weight low. We stock the standard sizes for all your rocketry projects.
  
  
• Balsa Bulkheads
  Also known as Balsa Nose Blocks. These are solid connectors that are used to prevent the ejection charge gases from reaching any delicate payloads your rocket is carrying. Made for small size tubes.
  
  
• LOC High-Power Couplers
  The LOC high power tubes demand some big diameter couplers. These couplers fit the standard sizes for large diameter tubes such as LOC, and MadCow Rocketry. Made from heavy-wall kraft (brown) paper. We also carry the LOC STIFFY Couplers, which are liners that fit inside the LOC couplers to make them even stronger.
  
  
• Blue Tube Couplers
  Blue Tube is used for high powered rockets where durability is more important to the builder. This is made from a vulcanized paper to give it very good strength, but it is not brittle at all. The wall thickness of the tubes is thicker too, so the couplers is much heavier than ordinary kraft paper.