I can't believe the price of spare catapult elastics,around 3-4 quid for many,I bought all the dedicated redicat elastic available many years ago and still have 11 lots,I have been on eBay and bought 2m of elastic to try for £4.76 post free,4m is £8.27,I will give it a try,2m equates to roughly seven catapults,this stuff comes in 4 or 5 grades,from extra light(what I bought)to extra strong.