Stickii Club offers three different types of monthly sticker subscriptions: Cute, Pop, and Vintage. The packs are differentiated by color: pink for Cute, aqua for Pop, and gold for Vintage. Each pack is $10 per month plus tax and shipping and comes with at least six sticker sheets and at least three stationery items.

Stickii Club Pop Pack May 2021 contents
I had to get this pack because I have been following @maruti_bitamin for a while and she designed four of the sticker sheets in it.
Light green plant bud paper clip, envelope with waves stamp, and a tiger jumping through a fire hoop notepad
The theme of this pack is In My Element. The stationery items included are 1) light green plant bud paper clip, 2) envelope with waves stamp, and 3) a tiger jumping through a fire hoop notepad designed by @lele_melele.
Fire-themed sticker sheet
The artist that designed the notepad also designed this fire-themed sticker sheet with a monkey juggling fire balls, a snake breathing fire, fire flowers, etc. I actually didn't notice the first time that the tiger has eight legs.
Water-themed clear sticker sheet
The artist that designed the stamp also designed this water-themed clear sticker sheet. There are cats, popsicles, umbrellas, etc. with waves on them.
Water @maruti_bitamin sticker sheet
This is one of the four sheets @maruti_bitamin designed for this pack. The theme for this one is water.
Fire @maruti_bitamin sticker sheet
This is the second of four sheets @maruti_bitamin designed for this pack. The theme for this one is fire.
Air @maruti_bitamin sticker sheet
This is the third of four sheets @maruti_bitamin designed for this pack. I am assuming the theme for this one is air because of all the moths.
Earth @maruti_bitamin sticker sheet
This is the fourth of four sheets @maruti_bitamin designed for this pack. The elemental theme for this one is probably earth due to all the plants.
Foggy mountain washi tapes sticker sheet
Of course there has to be a washi sticker sheet in the pack. I actually really like the foggy mountain theme, so I might actually use these somewhere.