These sponsons, the Double Beta, cost around £11.05 for a pair, and are suitable for larger tanks such as the Land Raider. Their shape makes them unsuitable for Baneblades (without modification, the Alpha is a better option) The sponsons don't some with locating pegs, so a good bit of eye-work and guessing is needed to ensure that they line up right, but it does make it compatible with other ranges of tanks with only a bit of work.
The kit doesn't come with guns, but it's very easy to add your own (a selection of weapons are also available from Blood and Skulls). The kit includes recessed holes for magnets, or you could glue weapons directly to the weapon mounts, which swivel left and right once assembled.
If you're after some tough-looking armoured gun-mounts, then these offerings will do a great job of that. The weapon mounts maybe slightly over-engineered, but that's airways prefered over an under-designed mono-part upgrade.