Extra Wide sand bags, these enable you to use less bags per tunnel and therefore often save money and time.
Coverage of your tunnel is more important than number of bags for example:
x4 50cm bags (cost £200) covers has 200cm of coverage where you would need
7 bags at 30cm or
5 bags at 40cm.
Wedge shaped Tunnel bags.
Nice large size bag high fill volume ideal for tunnel ends.