Remember

Once you pull the pin, Mr Grenade is no longer your friend.

While making sure I'd remembered that M26 is the correct designation for the "lemon" frag grenade I checked Wikipedia because there's a different designation for the M26 when it's got a safety clip.

M61.

The very familiar M67 is, in fact, an M33 with a safety clip.

What I learned, though, was there was an impact fused version of the M26, the M26A2.  It's kinda neat.  Throw it and it goes off when it hits something.  If it doesn't hit something hard enough, it goes off in 4 seconds.

The problem is the "hits something."

Like a branch or heavy brush.  Or if you fumble and drop it...

Oh, the M26A2 with a safety clip is an M57.

The impact versions of the M33 are the M33A1 and M59.

Is this confusing?  The way I've presented it, yes.

Lemon Grenade:

M26 fragmentation with 3-5 second fuse.
M26A1 fragmentation with 3-5 second fuse.  Improved fragmentation over M26.  L2A1 in British service.  DM-41 in German service.
M26A2 fragmentation with impact fuse.
M56 an M26A2 fragmentation with 3-5 second fuse.
M57 an M26A2 with a safety clip.
M61 an M26A1 with a safety clip.

Baseball Grenade:

M33 fragmentation with 3-5 second fuse.
M33A1 fragmentation with impact fuse.
M59 fragmentation with impact fuse.
M67 an M33 with a safety clip.  C13 in Canadian service.
M68 an M59 with a safety clip.