
Sounds weird, but the smooth bottom is a feature. I usually mix a small amount of acrylic into these cups so my mixing tool rubs against the bottom and it helps if it's smooth. The caps always remain locked. I am very happy with these mugs.

Large Capacity Looen Yarn Knitting Storage Tote - Portable Travel Bag For Unfinished Bulk Projects With Shoulder Strap & Crochet Hooks Case
28 Review

PACMAXI Sewing Accessories Storage Bag, Knitting, Craft Tools And Accessories Organizer, Roomy Carrying Bag For Sewing Tools And Accessories(Grey)
31 Review

ARTDOT Diamond Painting Storage Container With 2 Drawers, 96-Slot Bead Storage Bottles, And Tools Rack For Easy Access To Accessories
27 Review

Tebik 65 Pack Journal Planner Pens Colored Pens, 60 Assorted Colors Drawing Pens With 5 Different Stencils, Perfect For Dotted Journal Planner Writing Note Calendar Coloring Office School Supplies
29 Review

27" Monitor Acer Nitro VG270Ubmiipx, 2560x1440, 75Hz, IPS, black
37 Review

Full Grain Leather File Folder Organizer Document Holder Portfolio For Men, Moonster 13" 14" 15โ Laptop & Tablet Sleeve Case
32 Review

Handcrafted Leather Pencil Case - Elegant, Practical & Durable 8"X4" Design W/ Side Pocket & Keyring!
35 Review

BTSKY Colored Pencil Case Holder - 160-Pen Capacity Deluxe PU Leather Storage Organizer With Handle Strap For School, College, Office Watercolor Pencils Organization (Pink)
15 Review