Laser spars are made of aluminum tubing. The boom and topmast both use the same tubing so if your topmast fails it is worthwhile to hang onto the long bit for use as a spare boom. Note the boom should have an internal sleeve to reinforce the kicker attachment. If you buy an older boat check the sleeve is present, and fit a sleeve if it is not there. Dimensions of the boom sleeve are: 900mm long, outside diameter 44mm, wall thickness 1.8mm.
New spars come with stainless steel rivets holding the various fittings in place. Over time the aluminum can corrode causing damage and eventually spar failure. To help prevent this damage the stainless rivets can be drilled out and replaced with aluminum. These will cause less damage over time, although Aluminum is considerably weaker and the rivets will need to be replaced from time to time. The rivets should be inspected for wear and damage on a regular basis to prevent any nasty surprises. Corrosion inhibitor paste should be applied where stainless fittings come in contact with the aluminum.
During the quiet winter months it is worthwhile to check your spars for loose fittings or rivets and make sure they are not bent. Spars can last longer by changing rivets and also swapping ends on the spar.