10 shot self indexing magazine in .22 calibre, that will fit the following rifles;

NOVA VISTA LEVIATHAN
NOVA VISTA HP-900
NOVA VISTA BEHEMOTH
AIR VENTURI AVENGER

Features a complete polymer body w/ vinyl face and brass pin stopper. Spring loaded w/ a torsion spring and retained altogether by a steel hex drive c/sunk screw.
Works really well and reliable, just be sure to load up your pellets in the correct way in order for your pellets / slugs to index.
The center of the dial features a numerical index, so as to indicate how many rounds you have left, for quick reference. The oblong hole in the vinyl face is generous to allow ample berth to insert your rounds by.
The magazine slots in from right to left straight and nudges into place w/ a positive click usually.

Just watch out that, because this is a self-indexing magazine, that you do not double load a pellet / slug by pulling the pellet probe out from the magazine but not cocking the gun, then reinserting the pellet probe into the breech. This is one of the more common new user errors we've seen happen. Otherwise, if a minor were to use the rifle and repeatedly cock the bolt back and forward and jam the barrel up with pellets and slugs. This is also an issue we've dealt with once or twice. Normally you can make a plan by using a .22 ram rod and pushing the pellets out from the muzzle end through to the breech if you feel this won't jam your barrel up / don't want to remove the barrel. Otherwise, you'll need to remove the shroud, followed by the barrel, then push the pellets from the breech side, through the muzzle end. This latter method usually is recommended as this will be the least likely method of the two mentioned, that might cause damage to the rifling of the barrel.